My Sidewinder X8 need to be sent back for warranty purposes (and dunno when I can get it back), therefore I replaced it with a Roccat Kone (come free with Roccat Taito too from Athrun). Works very well, and my only grouse with the mouse is the significant amount of force needed to click the mouse wheel.
The Sidewinder X8 top-down side buttons is also probably better than this mouse (and pretty much everybody else) front/back side button.

And the Roccat Taito mousepad is definitely the biggest mousepad I ever had.