i'll chip in on this one... i have two suggestions:
a) avoid logitech like the plague. the hardware is usually good (except a weird obsession with usb mini-receivers over bluetooth) but the drivers are absolute crap, on both windows and mac.
i use a RadTech BT600 now -
http://www.radtech.us/Products/BT600.aspx
its brilliant. small, light, plenty of buttons, and it charges with a regular usb cable (with a regular mini-usb port) so you dont need to carry a special cable/charger when you take it on the road. you can also USE IT while its charging!