2nd vote for Logitech's T650 - no complaints and I like it's functionality better than Apples's Magic Trackpad at 1/2 the price.Yeah I read about alternatives but there's always some complaints. I know a lot of people here are anti-Apple but you can't deny their hardware is bullet proof; I bought the Trackpad for my girlfriends iMac and it's been faultless.
You can actually use the Trackpad on Windows but it loses many features.
http://www.amazon.com/Logitech-Rechargeable-Touchpad-Multi-Touch-Navigation/dp/B0093H4WT6