I tried a Microsoft trackball once; never could get used to the un-ergonomic setup (I don't have Andre the Giant-sized hands, which is what Microsoft made their trackballs for). I don't feel like burning the desk space for a mouse, so those are out.
These days the cordless are good, back when they first came out they were junk. Of course since both my Trackman's are relatively new even if I decide today my next pointers will be cordless that won't happen for 3 or 4 years.
Never like those huge central balls of the MS trackballs, I like keeping my button fingers stationary and I've never figured out how to do that with their design. The thumb ball is the way to go. I never liked mice period, seems I always have to do a lot of "rowing" (picking up and repositioning to go further in one direction) and that's just so much easier with a trackball than a mouse. Plus trackballs seem to confuse people so my computers get a little additional security.
It'll be interesting to see how this scrollball works out. There've been a lot of attempts in the last few years to handle horizontal scrolling and most of them have sucked. The industry seems to have by and large abandoned the effort lately. We shall see.