A couple of weeks ago I purchased IOGEAR's Bluetooth Mini Mouse and have been rather pleased with it so far. This is my third Bluetooth mouse and while the first (Microsoft IntelliMouse Explorer) was just horrible, the second (Logitech MX900) wasn't that bad, thus the obvious question of why I got another mouse. Beyond my usual urge to get the newest [insert gadget here], the only real impetus behind me getting the third one was size (and resolution).
Admittedly, the "Mini" part of the name is not a misnomer — this thing is tiny, but despite its stature the mouse is packed with features, a lot of which its much larger competition is missing. The feature that initially drew me to the mouse was the fact that you can charge it while using it. A USB 2.0 cable plugs into the front of the mouse and charges the rechargeable batteries while you work (or don't). The fact that there's no cradle makes it very portable and eviscerates the need to worry about whether the batteries are going to go dead; simply pop the cable into your bag and you're set. It also has an on/off switch so that you aren't wasting the batteries when not using it. While this might seem like an obvious feature, my first two Bluetooth mice were without it.
I should also mention that the mouse has 800 dpi resolution and can reach up to 66ft (instead of the usual ~30); why one would need the extra distance is beyond me, but you never know.