I sort of split the difference between the ergonomics of the trackball and the familiarity of mice. I got the MS Natural 6000 blah, blah, blah and have been happy ever since. I still wouldn't mid trying a trackball, and I, too, would probably go for the Kensington as it seems to have, or at leat the ability to emulate, all the features I enjoy on my MS. I haven't seen another trackball that has all the features my MS has that I use on a daily basis (forward/back buttons, scroll wheel with side to side scrolling, etc.).