After a couple of weeks of work, I've had the opportunity to try out a variety of commute methods. Here's an analysis of the daily round-trip:
Walking time: 50-60 minutes
Non-walking time: 30-40 minutes
Advantages: Relatively inexpensive. I get to walk through the city, which I love.
Disadvantages: Moderately slow. Long walk in winter, though I could add three bucks and change much of the walk to a Muni trip.
Walking time: Zilch
Non-walking time: About 40 minutes
Advantages: Fastest and cheapest
Disadvantages: Bay bridge on a bike, will suck profoundly in winter, no built-in exerise.
Cost: $6.50 plus parking, which is free if I get dumb lucky or $16 if I don't.
Walking time: Negligible
Non-walking time: 40-50 minutes
Advantages: Speedy, can haul stuff and people, dry in winter
Disadvantages: It's a fucking car. Parking is way expensive.
Cost: $11 plus $3 for Muni or a 45-minute walk each way
Walking time: 40 minutes
Non-walking time: 90 minutes
Advantages: Cruising across the bay totally fucking kicks ass, especially on the way home.
Disadvantages: Schedules are limited. It's expensive. Most time-consuming of the methods.
Conclusions: Bike vs. BART pretty much depends upon what time I make it out of the house. I'd rather take BART, but the bike is much faster. Take the car when I need it, but not otherwise. The ferry is a special treat.
Walking time is a huge plus for me-- I enjoy the exercise, and I enjoy walking through the city.