I've been doing this since the very beginning, and I also see HerO and HuK hold it the same way.
Concept
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So the plan here is using a 1 gate FE, so you're able to get a quick economic lead, this will allow you to get a mass of gateway units and a few immortals to crush the 1/1/1. So any 1 gate FE will work here but I'll give a build to the one Huk uses which allows you to get both gasses early so you're able to get a good sentry count
The Build
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-Only use 3 chronoboosts on the Nexus before taking the expansion
-Should have 24 probes before you make the Nexus
-Should have constant probe production before making the Nexus
-Should have constant Sentry production until you get to 3, Warp gate research should finish right after
9 - Pylon
Chrono Nexus / rally 13th probe to build the gateway
13 - Gate / Scout right afterwards
Chrono Nexus
14 - Gas
Chrono Nexus
16 - Pylon
Cyber after gate finishes
19 - Second Gas
Chrono Stalker and WG tech when cyber is done
21 - Pylon
Sentry after stalker
26 - Sentry
28 - Nexus
28 - Sentry
30 - Sentry
30 - 2 more gates
At the 6 min mark you should get the Robo (Need it at 6-6:10 if cloak banshees come)
After WG finishes, warp in a sentry and 2 stalkers. (You only want 4 sentrys, they generally suck for 1/1/1, you just need them for a few FFs and constant Guardian shield
So after the Robo finishes, you want to chrono out 2 observers, 1 to his base and 1 stays at yours, if cloaked banshees come, get a 3rd.
I will get an immortal right after the second Observer, depending on what I scout with the probe. If I still see no expo with the probe, I will also add a 4th and eventually a 5th after getting a few more probes.
I will usually try to get 16 probes at my natural if possible. But only chrono probes right after the Nexus is done at the natural (Assuming no early aggression has occurred), you need to cut probes against 1/1/1 and spend all chronoboosts on the gates
I will try to get 3 immortals out before the push comes, although I have held it with 2
-Should have 24 probes before you make the Nexus
-Should have constant probe production before making the Nexus
-Should have constant Sentry production until you get to 3, Warp gate research should finish right after
9 - Pylon
Chrono Nexus / rally 13th probe to build the gateway
13 - Gate / Scout right afterwards
Chrono Nexus
14 - Gas
Chrono Nexus
16 - Pylon
Cyber after gate finishes
19 - Second Gas
Chrono Stalker and WG tech when cyber is done
21 - Pylon
Sentry after stalker
26 - Sentry
28 - Nexus
28 - Sentry
30 - Sentry
30 - 2 more gates
At the 6 min mark you should get the Robo (Need it at 6-6:10 if cloak banshees come)
After WG finishes, warp in a sentry and 2 stalkers. (You only want 4 sentrys, they generally suck for 1/1/1, you just need them for a few FFs and constant Guardian shield
So after the Robo finishes, you want to chrono out 2 observers, 1 to his base and 1 stays at yours, if cloaked banshees come, get a 3rd.
I will get an immortal right after the second Observer, depending on what I scout with the probe. If I still see no expo with the probe, I will also add a 4th and eventually a 5th after getting a few more probes.
I will usually try to get 16 probes at my natural if possible. But only chrono probes right after the Nexus is done at the natural (Assuming no early aggression has occurred), you need to cut probes against 1/1/1 and spend all chronoboosts on the gates
I will try to get 3 immortals out before the push comes, although I have held it with 2
Scouting
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So scouting is one of the most important things to do in vsing a 1/1/1 or any early aggression in general, you MUST know when it's coming or you're going to be completely caught off guard, this goes for any sort of 2 rax as well. I will try to always poke up the ramp at the 3:40 minute mark to see if he's got 1 or 2 marines, if he has 2 it will mean no tech lab/reactor, and probably not going to be any sort of marine/marauder early aggression, since the 2 rax requires you to get an immediate reactor (or a tech lab) after building the first marine, BUT if you see 1 marine, poke up at 4:40 and see if there's 3 marines or a marauder, 3 marines meaning reactor. If you did manage to scout him first, and you saw the gas, AND you see a bunker, it's almost 99% tech.
So you might be wondering why scout after gate if scouting is so important? Well, the build doesn't really stray away from the original build no matter what you scout, rather it just gets you better prepared, so if you see a marauder when you poke up (1 marine, 1 marauder), it's most likely going to be a 1 rax expand from the Terran and he may pressure a bit, so you know you have to pull a few probes if he does, if your probe ever dies, immediately send another one, either to the watchtower or at the bottom of the ramp, as long as your able to see when he's moving out and what he has
So you might be wondering why scout after gate if scouting is so important? Well, the build doesn't really stray away from the original build no matter what you scout, rather it just gets you better prepared, so if you see a marauder when you poke up (1 marine, 1 marauder), it's most likely going to be a 1 rax expand from the Terran and he may pressure a bit, so you know you have to pull a few probes if he does, if your probe ever dies, immediately send another one, either to the watchtower or at the bottom of the ramp, as long as your able to see when he's moving out and what he has
Early Aggression
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So yes obviously taking a quick expo comes with risks, with proper micro you will be able to hold anything but it is hard, so if you don't have the good force fields and unable to micro back and forth, I'd probably look up another 1 gate FE, like getting a Zealot while the Cyber is building and chronoboosting stalkers out, and not take the second gas.
Against a 1 rax tech lab, marauder push, it's quite simple, you should pull 4 probes and just continue with your original build, if there's more marauders, you have to pull more probes, this is why you have to scout!
Against 2 rax, the whole idea of what you try to do is, STALL IT, you need to wait till your gates turn into warp gates so you can get stalkers out, and the reason why you save so much Chrono at the start is because you have to chrono the gates against any sort of aggression. The 2 rax itself isn't that hard to stop, it's the SCV building the bunker that can be hard, you need to act fast before it goes up, so quickly forcefielding half he's army, take it out then kill the bunker, or killing the SCV while you forcefield he's army off, it's all about micro/positioning.
In some cases you'll need to pull around half your probes if he has brought along a lot of scv's to. If the bunker does get up and he has alot of SCV's there with units, just sac the Nexus, your probably going to be behind but that's the risk of this build, you mis micro once and it can cost you the nexus and possibly the game.
Against a 1 rax tech lab, marauder push, it's quite simple, you should pull 4 probes and just continue with your original build, if there's more marauders, you have to pull more probes, this is why you have to scout!
Against 2 rax, the whole idea of what you try to do is, STALL IT, you need to wait till your gates turn into warp gates so you can get stalkers out, and the reason why you save so much Chrono at the start is because you have to chrono the gates against any sort of aggression. The 2 rax itself isn't that hard to stop, it's the SCV building the bunker that can be hard, you need to act fast before it goes up, so quickly forcefielding half he's army, take it out then kill the bunker, or killing the SCV while you forcefield he's army off, it's all about micro/positioning.
In some cases you'll need to pull around half your probes if he has brought along a lot of scv's to. If the bunker does get up and he has alot of SCV's there with units, just sac the Nexus, your probably going to be behind but that's the risk of this build, you mis micro once and it can cost you the nexus and possibly the game.
Unit composition and Army engagement
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I usually have around half Zealots, half Stalkers, 4 Sentrys, and 2-3 Immortals, you obviously need enough stalkers to deal with the banshees with the PDD there, while the Zealots meatshield everything and also causing splash damage to the marines if the Terran isn't target firing, try get your immortals to target fire the tanks, but don't just click the furthest away tank, sometimes your Immortals will durp against the marines trying to reach it.
It's obviously great trying to engage at the middle of the map to try force a PDD or catching a few units off guard, if you force a PDD, it's almost an instant win.
Although, I will only do this when I see him moving out, I will never just have my army chilling in the middle of the map just incase 2-3 banshees come into my main and I won't have enough stalkers to deal with it. Try to spread as much as possible.
So you're going to want to kite as much as possible with stalkers, you may be able to pick off some SCV's or even a banshee
It's obviously great trying to engage at the middle of the map to try force a PDD or catching a few units off guard, if you force a PDD, it's almost an instant win.
Although, I will only do this when I see him moving out, I will never just have my army chilling in the middle of the map just incase 2-3 banshees come into my main and I won't have enough stalkers to deal with it. Try to spread as much as possible.
So you're going to want to kite as much as possible with stalkers, you may be able to pick off some SCV's or even a banshee
What NOT to do
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So I always hear people theory crafting builds that 'counter' 1/1/1, so I'll give you some builds not to do
-1 Base Collosi
Yes I know you all love Artosis and I always hear him stating 1 base collosi crushes 1/1/1, except it doesn't, infact it's probably one the worst builds to do against a good Terran, if it's not far positions, the Terran will actually just be able to contain you with bunkers and tanks, before your able to get your Collosi out and that's pretty much game over, he'll be able to take an expo and start producing vikings, you also won't have a good stalker count, so when you try to engage a good Terran will target fire the stalkers, leaving you no anti air units, so banshees reign supreme
2 gate robo into phoenix (After scouting 1/1/1)
This build absolutely crushes 1/1/1 if the Terran moves out to soon with not so many marines, but if Terran sees them phoenix, or just decides to push much later than usual and gets a ton of marines, you're screwed, marines melt zealots and phoenix when there's a lot of them, and that's all your gonna have if your going phoenix, especially after getting a robo
Basically staying on 1 base in general = bad idea, Terran will almost always have an advantage on 1 base vs 1 base just due to mules and being able to float there main to the natural if the minerals run out.
-1 Base Collosi
Yes I know you all love Artosis and I always hear him stating 1 base collosi crushes 1/1/1, except it doesn't, infact it's probably one the worst builds to do against a good Terran, if it's not far positions, the Terran will actually just be able to contain you with bunkers and tanks, before your able to get your Collosi out and that's pretty much game over, he'll be able to take an expo and start producing vikings, you also won't have a good stalker count, so when you try to engage a good Terran will target fire the stalkers, leaving you no anti air units, so banshees reign supreme
2 gate robo into phoenix (After scouting 1/1/1)
This build absolutely crushes 1/1/1 if the Terran moves out to soon with not so many marines, but if Terran sees them phoenix, or just decides to push much later than usual and gets a ton of marines, you're screwed, marines melt zealots and phoenix when there's a lot of them, and that's all your gonna have if your going phoenix, especially after getting a robo
Basically staying on 1 base in general = bad idea, Terran will almost always have an advantage on 1 base vs 1 base just due to mules and being able to float there main to the natural if the minerals run out.
Alternative builds
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So I haven't actually tested these builds that much against 1/1/1 but they have worked for me.
3 Gate expo
Just the standard 3 gate defensive expo, and of course get the robo at around the 6 minute mark, and I deal with it the same way as the 1 gate expo, try chrono 2-3 Immortals if possible while getting a 4th gate (5th he pushes later)
2 Gate robo, expo
I've seen Puzzle do it a few times, where he starts chronoboosting Immortals out, right after he scouts the 1/1/1, and just gets 3-4 Immortals when the 1/1/1 comes and crushes it, but lately I've seen him go for a quick Stargate as the Nexus is warping in for phoenix, although this seems really blind, and risky. So I wouldn't recommend it.
Again, I don't do these builds that much anymore, but there much safer to pull off and I've had success with both of them against 1/1/1
3 Gate expo
Just the standard 3 gate defensive expo, and of course get the robo at around the 6 minute mark, and I deal with it the same way as the 1 gate expo, try chrono 2-3 Immortals if possible while getting a 4th gate (5th he pushes later)
2 Gate robo, expo
I've seen Puzzle do it a few times, where he starts chronoboosting Immortals out, right after he scouts the 1/1/1, and just gets 3-4 Immortals when the 1/1/1 comes and crushes it, but lately I've seen him go for a quick Stargate as the Nexus is warping in for phoenix, although this seems really blind, and risky. So I wouldn't recommend it.
Again, I don't do these builds that much anymore, but there much safer to pull off and I've had success with both of them against 1/1/1
Summary
Even though it's a long guide, once you get used to the build and how to scout, etc...It all becomes very easy, not really gonna comment whether I think it's OP or not, but I don't really understand all the whine, I watch Huk's stream all the time I see him holding it off easy against all the top Koreans, and pretty much does the same build as me (I think). Anyway first guide I've written so probably a few mistakes, feel free to ask questions too.
Replays
I'm gonna start saving all my replays defending 1/1/1, I've only got 1 right now but it's pretty clear how to defend it.
Me defending 1/1/1
http://www.gamereplays.org/starcraft2/replays.php?game=33&show=details&id=229038
Huk defending a 3rax from MKP with the 1 gate FE
http://www.gomtv.net/2011gstls1/vod/65784