Depends on the game. No matter what game however the performance is light years better than FragFX. I have one of those too.
COD4 feels like playing on a PC. I don't feel any lag whatsoever.
Uncharted is a little rougher, not as responsive. That is the game however, not the XIM. No matter what sensitivity I put things too, I can't exceed the programming of the game and make the cursor move faster. The game just has a sluggish control for aiming.
Resistance is kinda in between. More responsive than Uncharted, but more sluggish than COD4.
If there is one thing I like about FragFX though, is the combination of a stick for movement and mouse for aiming. Also having 6 axis helps with some games.