If you wear a full mask, be prepared to not be able to use the gun's sights, unless they're REALLY high. I wear a pair of Uvex Tac-1 Goggles
, and nothing more.
One of the guys I play with uses the ESS Turbofan Goggles and swears by them, but they have a $220 price tag on them. Everyone else uses Airsoft Mech-Goggles, which I tried out, and they're not bad once you get used to looking through a screen. They're heavier than regular Goggles though.
Only one of the guys actually wears the full mask, but he melted the right side of it down so that he could still aim while using it. It too is an Airsoft Mesh Goggle/Facemask, not a Paintball mask. You can get them from Xtreme-Tactics
The only time a full mask would be a must is if you're doing CQB with 350-400fps guns.