Summary: I had been looking for a replacement for Apple's skittish Magic Mouse because I'd often set the screen scrolling just by grabbing it. And successfully manipulating a right-click was like doing brain surgery - arrghh! I already had replaced Apple's tiny, Chiclet keyboard with a full-fledged one from Logitech and was hoping to find a mouse that used their unifying USB receiver - not many of those do so for the Mac. So I ended up looking for a Bluetooth model.
Summary: I have used the M555b mouse for the last 8 months. I looked at reviews before I got it and while the reviews were generally good, there were some complaints that the cursor wandered, the batteries didn't last long and that the connection wasn't very reliable. My experience is that none of these complaints were anything to do with the mouse. I have found it to be extremely reliable, precise and a joy to use.
Summary: The not so great SetPoint mouse software included is incompatible with AutoCAD. Software conflict caused mouse to stop working and only solution possible (due to zero support from Logitech) was to remove mouse software from system. Mouse seems to work well without SetPoint but you lose the paid for bells and whistles that would have been nice to have. Do not like having to use the small button in front of wheel to pan. Does not work well with Excel.