Thanks for the referral to Trackpad++. I sent the guys at Trackpad++ an email asking them if they would be able adapt their driver to the Magic Trackpad. I assume it would be quite a simple adaptation considering how similar the Magic Trackpad is the the Macbooks' built in trackpads.
If you would also like to request this feature send them an email at support@powerplan7.com
I offered to donate if they would make an effort at creating a more polished driver for the Magic Trackpad, and would encourage you all to do the same (it'll give them some incentive even if they never plan on owning a Magic Trackpad themselves).
If anyone already has their Magic Trackpad, could you do me a favor and see if Trackpad++ already has some level of compatibility? I have no idea if the driver will be able to identify the Magic Trackpad since it is using bluetooth and a slightly different hardware configuration, but it is worth a shot. The downloads for Trackpad++ are here:
http://trackpad.powerplan7.com/downloads.htm