I'm using Xtremeguard, and I'm not thrilled with it. It fits well and stays in place. But I'm not especially careful with my phone and the screen regularly comes into contact with keys, change, etc. This results in dimples in the screen protector that either don't go away or go away so slowly that new one are still building up.
So maybe I should say that this isn't the best option if you are careless with your phone. Somehow I managed to treat my original Moto Droid the same way for almost two years without a screen protector and without a scratch. But the G2x screen has not fared as well, and Xtremeguard has not proven to be the answer.