I bought one today. On my XP machine, with no extra configuration, I can use the ball as a vertical mousewheel, left, right and middle buttons.

I cannot use the horizontal mousewheel action of the ball or the squeeze buttons on Windows XP.

Is anyone working on a Windows XP driver? The ball is a really nice change from a mousewheel. Till now, my favorite mousewheels were the MS Blue Optical(almost no resistance) and the Logitech MX510. The scrollball in the Mighty Mouse feels much more granular.

First app I’m going to play with once a driver exists for the horizontal scroll ball? Google Earth.

Apple Mighty Mouse Product Page
Apple Mighty Mouse Compatability Chart

I picked up the Logitech MX510 Mouse that stiill has been talking about. I’ll start using it tonight.