I've tried several and none have been great. This is my first mac and I can't get used to a 1 button mouse, so I've been searching for a decent 2 button/scroll BT mouse.
The Logitech MX900 was no good - tracking was lousy and sluggish, even with software to tweak the speed.
MacMice - tracks great, but hard to click (have to hit it just right). Also, the red LED shines throught the thin plastic shell - all that blinking was a huge distraction when I was trying to type (maybe I just drink too much coffee), Also, constrution feels cheap. A mixed bag.
I'm now using the Bluetake BT500, which works great, but is tiny. Not sure yet how I like that (using it with my desktop).
Actually, the best BT mouse I've used so far in terms of reliability and ergonomics has been the Apple. If only I could get used to the one button design....