I've been using trackballs since the early 90's being in the architectural industry. I've never been able to go to a mouse, its just uncomfortable to me. Of all the trackballs I've used, the MS Optical Trackball Explorer is the best. Here is a link to the product page (http://www.microsoft.com/products/in...f-f087c17ffd30 ). It has 4 buttons plus the scroll wheel.

I've tried the Logitech Cordless Optical Trackman, but didn't like the buttons. They aren't like regular mouse buttons. I also don't like the location of the scroll wheel. I prefer to have it usable by my thumb.