Protoss fanboi here too. I got it for the SinglePlayer, I'm not that competitive in multiplayer games. I played a bit but after some games with T everyone just goes Mass MMM, which just pisses me off that they can counter pretty much every unit you throw at em with 10 stimpacked marines and a medivac above em... Also the taught that they can drop them wherever they want makes me go turtle mode and that ain't working...
The trick to beating MMM is to keep the pressure early and out macro-ing him. I'm only just learning how to macro effectively, but it has helped me a TON with my PvT games.
Also, unit counters (NOT TO BE USED AS A MOAB) that are effecitve (WITH SUPPORTING ARMY) against MMM are High Templars (Psi Storm DEMOLISHES marines) and Collossi. I suggest a heavy Zealot front with Stalker/Sentry support when using either of those units.