I used a Boomslang 2000 for 7 days (my friend told me to give it all the time I could before I said I didn't like it, so I did) and promptly went back to my opitcal mouse.
Yet, it's not for the movement or smoothness or anything, it's the uncomfortable feel the mouse has. I simple HATE the design of the boomslang. The mouse itself is smoother and much more accurate than even my new optical mouse (and I've tried them all). I just wish they'd adopt a more ergonomic design.
If you want a good optical mouse, I suggest the $30 one at your local Best Buy, or the Logitech one (it's blue.. can't miss it, blinking red light on the box). I've used both and while I like the feel of the MS mouse, the Logitech's isn't much worse, and it seems to be a bit smoother when I play Half life.
Hope that helps..