I use both the Apple Bluetooth Mouse (at work) and the Logitech MX900 (at home). I like them both. The Apple Mouse uses regular AA batteries and lasts a long time while the Logitech uses rechargables (meaning you'd have to drag around the base for charging, even if, like me, you're using the bluetooth on your Mac to connect to the mouse) which need to be recharged every few days.
The Logitech has more buttons however, and while not officially supported on a Mac, the buttons can be mapped to Exposé functions, and that works quite well.
I'd say, if you're looking for something you can throw in your laptop bag to use on the road, I'd go with the Apple mouse, unless you need the functionality of additional buttons.