Originally posted by Nix 
stay away from microsoft mice with tilt wheels.  theyve removed the clicky-ness from the scroll wheel, making it a big pain in the ass
Oops, my bad.  I should have mentioned that.  The ONLY thing the damn tilt wheel is good for is side-scolling Excel sheets.  Apart from that, they are pretty solid.
My rating, from constant daily use:
1 MS Explorer - slick and well-made (apart from the sucky tilt wheel)
2 MX700 - nice, but the programming sucks compared to MS
3 Apple clear - great to use, but only 1 button (Wake Up Apple!)
4 Wacom - sucks, but the pen is excellent