I have a Logitech cordless trackman. It's OK, but not very good more than about 3' from the computer.

I have an Intellimouse trackball that I like, but it's not wireless.

I have a Kensington Expert Mouse Pro (actually a large heavy trackball), that I use most often. It's wireless, it has lots of programmable buttons, and works with 9 or X. It's more expensive, but I think, worth it.

Lampie