Currently, I think we're out of luck in terms of special OSX mouse drivers, although Kensington has a beta X version of their drivers available (I tried to install the Kensington drivers to see if they would work with my Logitech Marblemouse, but no go. Long shot anyway).
However, Alessandro Montalcini, author of the excellent USB Overdrive shareware for the classic Mac OSes, has stated on his website that he is hard at work on a version for X. In 9.1, USB Overdrive shines the factory drivers for my Logitech like nobody's business, so I have high hopes. See
http://www.usboverdrive.com for more.