Steve Bobosky wrote up a cool blog posting on how to get User Affinity in to ConfigMgr 2007 right now, rather than waiting for this to arrive in the form of v.Next. Steve's going to hand over the goods in separate postings, with this, the first, kicking things off:
http://systemcentertools.blogspot.com/2010/05/user-affinity-now-part-1-setting.html
Is seriously worth a read, even if you won't use it, just to see how he's managed to map everything together to provide User Affinity (Mapping users to devices\machines)
Steve pretty much defined mapping users to devices\computers in the form of SLAT for SMS 2.0 and SMS 2003, and then along came Asset Intelligence in ConfigMgr 2007 which did roughly the same thing (but as Steve points out, username exceptions are not considered in AI but are in SLAT)
Nice work Steve, always appreciated.