I've been using the intelli explorer (the old one w/2 buttons on the left) for quite a while now. It has a faster rate when you use it via usb and it is not compliant with the "mouse rate o/c'ers" in the ps2 slot. How ever I have never had a problem with it as far as fps game go, and i don't find it to be worse than the ball. That razor mouse isn't all that and a bag-o-chips either, i used my friend's for a month or so and decided it's not worth the money. IMHO the two extra buttons on the mouse are really handy for fps's. To top it off it has a 5 year warranty, which is good, they seem to break down every two years, i've taken mine back twice, but the second time was just cause the buttons felt to soft (over use hehe).
Guess that's it for now, ball mice don't serve my mad fps skills any better.
oh, ps to the intelli users out there, don't update ur mouse drivers to the 3.x cause it brings down your rate by 20 or so. [i get about 130hz w/my optical]