100% PC gamer here:
GT750 got this primarily for input lag. I'm one of those FPSers that REALLY notices this. Try spinning around and shooting something on a fast LCD, then try spinning around and shooting something on a >30ms projector == a whole different game. Lag is why the (Battlefield3) TVM is difficult for people to master. Internet latency is a whole different bag of lag, so it's not comparable (i'll discuss if someone wants...)
Games:
Battlefield3 (not worth the 3D, IMHO, at least on my setup and with builtin drivers)
Battlefield2: Project Reality (3D crashes for me, but I play this competitively so I wouldn't use 3D anyway)
GTA4 (REALLY wish there were a first person mode, this is RAD in 3D)
Diablo 3 (input lag doesn't matter here, 3D is pretty cool but not "holy sheeit!", though the art is amazing)
Fallout 3 (playing this again because of 3D, totally worth it. Input lag doesn't really matter since it's not multiplayer and is generally easy)
Arma 2(haven't tried this too much, but 3D looks sweet once you get the settings right. Input lag matters here.)
Counterstrike: Source (I haven't tried this at all... it's so twitch, that on a huge screen i doubt it would be better. As someone mentioned before, your eyes have to move so much farther == slower reaction == being one of the suckers again)
Quite honestly, I think the ideal use of a projector is to sit up real close (~4 ft with a ~120" screen) and turn up the FOV, so you get a "wrap-around effect". Sitting far away in GTA4 with 3D on is nowhere near as cool as sitting close with 3D on. That being said, I wouldn't play that way with twitch FPS games, unless I'm in the mood for being shot a bunch.