I use a mouse all day as well. At work I exclusively use a Microsoft Natural Laser since it came out 3 or 4 years ago:
The idea is that it rocks your hand off the carpal tunnel and prevents CTS
The wife didn't like such shenanigans, so at home we have a Logitech M505. The tracking is great, the feel is good, the size is right.
I'd go to a big box store, put your hand on all the samples, and then buy the one that feels nicest. (how we ended up with the m505)