This is the most recent official BART
press release. Basically, there is no date set, but once the system gets handed over to BART, BART will then require at least a month's worth of testing (presuming there are no problems--unlike the AirTrain accidents during testing at both SFO and JFK) before it can open up the system to the public.
Oh, and
Eastbay1K, give the Bay Area some credit--its only been 30 years since this idea has been first proposed.

Specifically, the first mention of rail access to SFO was in the San Francisco Airport Access Project Report, issued in 1972. The 40 year figure is for JFK... (sorry, this is my thesis topic, so I'm engulfed in data on this very isse).
[This message has been edited by EnhancedByCO (edited 02-05-2003).]