It seemed to work fine for me, it was pretty much instant from what I remember. I do recall having to tweak the advanced settings in the program to change the way it captures and releases mouse input. (can't totally remember why, I think there was some weird flicker or something like that)
The only other consideration, is if you're going to play a fullscreen game with it activated, you have to press scroll lock to lock the cursor onto the screen the game is on (otherwise the game will randomly lose input focus when the cursor gets switched "off screen").
