I'm using the Logitech M570 under Windows, Linux and FreeBSD. I haven't tried the others, but absolutely love the M570. It's battery life is unbelievable. One AA battery, M570 used Mon-Sat and the battery has lasted over a year and still shows 200+ days remaining! In contrast, my wife's Apple Magic Mouse needs two batteries every 2 months. I also use the M570 to control my media player from the couch, while my MacBook Pro is plugged into the TV. As Tracer mentioned, it is thumb based, but I had no problem with that. Mouse scrolling is nice and easy too, though I want to still mod mine (like I've done with my Logitech MX510 mouse) so the mouse wheel is smooth - no ratchet feeling on the wheel. Ball rolls very smoothly, cleaning is easy. I highly recommend the M570.
I'm a bit of a trackball fan. out of the ones in this poll, I have the Slimblade, the Expert, the M570 and the Orbit, (except I have the Orbit with the scroll ring). I'm curious enough to try out the CST. Out of the bunch that I have, the Slimblade is my favorite. The M570 also sees a lot of action, as I use it for my HTPC.
Has anyone here had experience with the CST2545W in contrast to the Kensington Expert mouse? I hear that the CST is overall much better, so im hoping to see it ordered on here. My Kensington Expert mouse was always sticky, but after a while it was so bad (despite cleaning) that it was practically unusable. I ended up breaking the plastic clips that hold the plastic bearings in place, so im in the market for a new trackball (I like them better than regular mice). The CST mouse is supposed to have stainless steel rollers btw.