For me, I was starting to get wrist pain with my mousing. I purchased 12 different mice, tried them all out, keeping note of how I felt in my hand. I eventually found out that really large mice is what work for me. The M$ intellimouse explorer specifically. The MX revolution, and all the other fancy mice weren't as good as the huge honking intellimouse explorer. The huge thumball mice were also good, but I didn't have the patience to learn them.