Before you give up on it, check the bottom and make sure that there's not a hair or a piece of fiber lodged where the laser lense is on the bottom of the mouse. Also, try a new mousepad as well (make sure that it'll track right with a laser mouse). Could it be the battery (i have 0 experience with cordless)?
If all of that fails, i love my
MX518 (i know it's corded, but i still love it

)