I have a Genius cordless, it's a bit hevier than ussual but it rocks for designing, i think that little extra weight adds to a better control of the mice
now, batteries are a royal pain, i got Panasonic rechargable batteries but i didn't know the're different kinds of them (got something to do with mA) and these last only a week so be carefull when choosing rechargable batteries
Erotic Design