A late addition to this thread:
With the MC-303 Controller software you can tune the drumsounds. It's not anything near a real 909 or 808, but it's a great addition, although the user interface is kinda messy and the program somewhat erratic... http://www.ping.be/insitu/insitusof.shtml

And a cheaper way of getting the 808/909 sounds than a Novation is ReBirth. http://www.propellerheads.se/