Listen to LiquidSoul. He is right.
I have both the Logitech Cordless Freedom Optical (keyboard and
mouse) and the MX700.
The Cordless freedom works great, but the mouse does have a
lag (although small) in gaming.
The MX700 is a superior mouse with no lag in gaming.
I think the Logitech hardware is nice, but the drivers SUCK. The
buttons are not supported when gaming. I can't use my MX700
when playing UT2003 because I can't program the buttons.
If you are looking for a gaming mouse, don't buy Logitech.