Despite some recent financial woes I had to re enter the mouse market this last week due to the pain caused by my old computer mouse.
I had a Logitech Wireless Mouse M310 and its small size was really hard on my hands causing severe cramping in my fingers and wrist.
(it came with the keyboard, a Logitech MK520 mouse/keyboard combo set)
I heard Trackball mice were better for you if you experience pains in the fingers or wrists when using a mouse so I now own one.
I have to say it works pretty well for my issue, my wrist and fingers on my right side are now feeling better after my hands leave contact with the mouse.
Its a Logitech Wireless Trackball M570 and while it will take time getting used to and the ball to get broken in I say its a very good mouse all things considered.
I will say it is very weird to work with at first but after some time it does get better after playing around with it.
I am sure there are some trackball users that might give me feedback here