Shield Batter - placed next to another structure, it will not allow small units like zerglings/marines to squeeze between the structures. It will add a strategical option for protosses with a fair trade off.
Scout - The vision range upgrade is exchanged for detection ability upgrade. Now scouts can see invisible units and provide alternative detection route for protoss.
Dark Archon - Its born with 85 initial energy, so its a better reactive unit vs mutalisks and carriers
Queen - can infest protoss gateways and they can produce infested zealots (same values as infested terrans) but without the ability to move the gateway around the map. So, this ability is not completely useless in ZvP match up.
Queen - Parasite can not be destroyed by medics. So it can be used in ZvT too.
Medic - Restoration cost 150 and is a small AoE, like 1/4 of plague area so it can fight it off to some extend but on a high price.
Ghost - It comes with a researched invisibility upgrade. The unit is too costly anyway and has too many costly upgrades to become even remotely useful, so getting one of the upgrades for free might make it a more desirable option.