The equation seems to have changed, however. First, Stanford recently brokered a deal with CalTrain, such that I (and all other off-campus grad students) get a nice little sticker on my student ID that the conductors will purportedly accept in leiu of a ticket -- and thus, riding the train is now about $2.50 cheaper than it used to be. Second, I've got a laptop from work now, and much of my work is now stuff that I can fairly easily do on it, so some of the transit time counts for work. This morning, I got the timing just about right, so it was 45 minutes door to door -- about 20 minutes longer than my driving commute, but 25 minutes of it was work (albeit with small interruptions to get on the train, and then off the train and on the bus), so it was about the same. And there's the advantage that all of the remaining time was walking and thus exercise, rather than 10 minutes walking and 15 driving.
I think I shall ponder working this into my plans a bit more often. The remaining problem is that my laptop is rather heavy for walking around with, but I could get a backpack if that becomes a notable problem.