Adel uses this opening almost exactly. I can't tell if he keeps 3 probes on gas during the zealot+stalker poke. I like to pull 1 off to mine gas with just 2 probes for a minute. With the stim nerf in 1.3, you can also start going zealot/sentry much earlier against bio, and Adel wisely starts sentry production before his nexus completes. Adel also does a very cool transition where he goes 3 gate, then forge, then 4th gate, then takes his 3rd nexus. The weaknesses in that transition are that it's hard to shut down drop harass and without a robo, you don't have scouting, but Adel quickly techs blink to deal with the drop threat. I think he should have research hallucination to allow better scouting tho. Anyway, it's awesome, and 1 gate FE can beat MVP.
This OP was hilariously out of date, so I'll update a bit.
The goal behind this opening (1 gate FE) is to sacrifice tech in order to safely secure an early economic lead against most Terran openings. Against Terran FE builds, you will typically find yourself even in economy with a military advantage. There are a lot of good players that believe this opening to be unsafe, but I used this opening in ~90% of my PvT's in Top 200 NA ladder, and despite the fact that most of my opponents know what's coming, I do pretty well vs T. Minigun is a lot higher on the ladder than I am, and he says he still uses 1 gate FE a good amount. If you're having trouble defending your expo in platinum, it's probably not the build's fault.
Here's how I execute 1 gate FE:
I open with a 13 gate and scout after my gateway. I spend all of my early chronoboost on my nexus, and my gas and core timings are standard. I make a zealot @100 minerals after starting my core and a stalker and WG research when the core completes. I then take 1 probe off of gas and place it on minerals. 2 probes mining gas is plenty to give you the stalkers you'll need to defend, and I find that making sentries this early is an easy way to ensure a quick loss.
With my probe scout, I'm first looking to see if T is playing standard (normal barracks timing, proper SCV count, 1 gas taken at normal timing timing). If T is doing something weird (hasn't taken gas, has stopped SCV production), respond accordingly. Otherwise, if everything looks normal, continue as planned to FE. I keep my probe in T's base to see if he'll show me what his next building will be, and just as importantly, what he does with his barracks after his first marine.
Ideally, I want to rally my first stalker to my zealot outside T's base to attack with these two units for scouting. If T builds a second marine or a reactor after his first marine, I know I can attack with my first zealot and stalker without fear of concussive shell completing before I get there. If I see a tech lab, I need to play more defensively. If T won't let me see what he does next, I prepare the zealot+stalker poke while I try to figure out whether he made a second marine with my scout probe. I'll sac the scout probe if I have to before attacking--if T's still denying your scout with 1 marine, there's a good chance he's waiting for you to suicide your units into his marauders.
I spend 1 chronoboost on my gateway and the rest on WG research and/or probe production depending on how safe I feel. The nexus should be started at 30/34 food with 400 minerals right before your zealot+stalker reach T's base. If I suspect heavy pressure, I cut probe production at 30/34 to quickly get 2 more gateways, 2 more stalkers and a pylon. Otherwise, I fill the available 4 food with 2 probes and a stalker while getting 2 gates and a pylon. Try to time WG research up with the completion of a stalker to optimize production. If T isn't making marauders, you'll need a robo facility for observers soon after you've started your third gateway.
Your WG research should finish just before your nexus completes, so use this as a timing cue that you'll need to transfer workers shortly. This is also when a 2-rax expo or 3-rax all-in will hit. If there isn't MM attacking your nexus, you want to send one of your transfer probes to camp T's natural. THIS IS VERY IMPORTANT. Terran players LOVE to do late all-ins vs 1 gate FE, and this scout probe will tell you whether an all-in is coming. If there's no expo when your probe arrives, you need to get 2 more gateways (5 total) ASAP. If you wait for your observer to scout the all-in, it will be too late. There are good non-all-in builds Terran can do that won't have taken the natural by the time your probe arrives (siege tank expand, for example), but scouting a lack of an expo at this timing tells you that an all-in is likely, and you'll need to get the extra gateways right away in order to be safe.
If a minute or two pass and there's still no CC floating toward your probe, you know an all-in is coming, so you can cut probes and mass enough gateway units to defend. Anything that holds the push will win the game, so you don't need to worry about saturating 2 bases. If you cut probes at 40 and hold the push, you've won with 40 probes.
If a CC floats down a minute or two after your probe arrives, you can relax. Hopefully you haven't started your probe cutting. Your observer should be arriving a minute or two after your probe reaches T's natural, so by that point, you'll know for sure what T is doing.
A few random tips:
-Zealot-stalker is pretty good against low numbers of marine marauder. Just execute cleanly and micro well. It's pretty rare that I'm forced to pull many probes. Let your nexus tank for a bit if you need some extra seconds to warp in units, but don't let him finish a bunker.
-If T attacks with a small number of marines+marauders, this indicates a bio expand. If you micro well, you can clean up a good portion of his attack with minimal losses and counter. I like to grab a second gas and go for a 5-gate semi-all-in, particularly on maps with open naturals that are difficult to bunker.
-If you don't think you can break a bio expand, you'll want to get collosi quickly. Some people like chargelots with upgrades, but I find that a 2 base bio ball just doesn't allow you enough surface area to defend effectively with zealots. Storm comes too late.
-Regarding the compositions you want to shoot for against various all-ins, zealots are the way to go against anything but blue flame hellions. If there are banshees, grab just enough stalkers to kill the banshees after your zealots clean up the ground army. If there are medivacs, you'll need sentries to let your zealots catch the MM. Blue flame hellions are just pretty ridiculous against this build tho. That's ok--now that medivacs are slower, nexii are harder to snipe with drops, tanks do 35 damage to light, and repairing SCVs no longer make thors invincible, Terrans need some OP unit to abuse the crap out of. We can spot them a stupidly fast unit that, in pairs, can 1-shot 20 probes at a time and also shreds through zealots, our most cost-effective unit....
-If you still don't know what T is doing after making your first observer, you'll probably want to start a second. It's super annoying to lose 10 probes to a cloaked banshee because your first and only observer just reached T's base.
-If your probe reaches T's natural and hasn't spotted a push or an expo, consider moving some stalkers into your main. Banshees or hellion drops are probably on their way. Don't move everything tho. Terran players are sneaky and like to hellion drop your main while sending 2 more hellions to your natural.
-If I'm feeling amitious later, I might update some replays. Until then, enjoy the same old replays that have been here since August.
Replay added 3-1-2011 against NA Top 100 T:
Replays against early barracks pressure:
(New replay 8-26-2010. I was at ~900 diamond and opponent was slightly favored. T brought SCV for bunker but failed to deny my FE. He later brought SCVs for an all-in, it wasn't really that close. You'll notice that my timings were slightly off--late on gateway, and forgot to start warpgate when cybercore finished, but the pressure wasn't anywhere close to breaking my FE)
I'm not a particularly good player, but this build has held against almost everything I've run up against. If you really can't micro/macro at the same time, then this expansion will be tough to hold. In the hands of a good player, however, I think T's only good response is to expand as well.
Here's a replay of me playing incredibly poorly and still beating a cloaked banshee rush:
IMO, this build hard counters cloak rushes.
And for those of you who are concerned about how a 14-gate will deal with cheese, here's a replay of a 14-gate (it was even late) against a proxy reaper cheese from a 1200 Terran:
It's about to get a whole lot easier to hold that cheese with the nerfs to reaper and bunker build times.
One more update:
Since people have continued to ask for help defending against marine-banshee-raven all-ins, here's a couple replays:
I scout with a probe for an expo from T, and if it's not there, I start preparing for an all-in by grabbing extra gates. When my obs confirms the all-in, I cut probe production and max out on zealots and stalkers with chrono. Make sure you have 1 or 2 sentries for guardian shield. By the time T's push finally hits, your army is so big that the PDD doesn't even matter.