I've got a Kensington Pro Elite and I really like it. Works great with OS X right out of the box and even better when you download the OS X beta of Kensington's Mouseworks software. Very accurate, it looks good (yea, the glowing blue light is a little much, but kinda cool I guess) and fits my head very well. Plus its got an ambidexterous design, unlike the more expensive MS Intellimouse. This is important if you have a lot of people sharing a computer.