I've gone whole-hog to trackballs over the last 6 months. The Logitech Optical Marble Mouse (easy to find @ around $15 NIB on ebay) works so well and saves me so much hand pain, I've now bought 4 of them.
I miss a real scroll wheel, but assigning the left-side sub-button to ball scrolling works okay. The precision and feel are awesome. My home computer still has a mouse, and every time I touch it I just go AUGHHH, so I bought another two tballs and have called it a day.
The only crappy part is, if I have somebody sit down at one of my machines, they often spout for a few minutes about how they "can't use a trackball"... Of course, most of them are asking me where to find this one at the end, so...
hehe