From Alessandro Levi Montalcini:
All it does right now is to swap the Windows and Alt keys so that their physical locations match the Command and Option keys on Apple keyboards. All the current Microsoft USB keyboards should be supported. The driver matching and loading process can still be a little tricky under Mac OS X, and you may easily find yourself using the standard Apple driver even after rebooting your machine. Here are a couple of things you should try before giving up: - Unplug the keyboard and plug it back into a different USB port. If you only have one USB port, you can try to plug it back into the same port. - Try to unplug the keyboard, restart your machine with no keyboard connected, and then plug the keyboard back. Try not to use the same USB port you were using when you unplugged the keyboard, if at all possible.