I think the BART to SFO is a good idea and should have been built in from the start. I'm not convinced that BART, Caltrain, bus, HSR, local rail all have to converge on one spot in San Francisco.
CalTrain has 55,000 daily riders. AC Transit 15,000. BART, a lot. Are there any economies of scale of putting all those people in one place? Does this density bring anything useful?
CalTrain connects with BART in Millbrae. AC Transit connects with BART in many places. The Capitol Corridor connects with BART in Richmond. Does this need duplication in SF?