Driving is the fastest by far. Traffic is backed up the opposite direction (going to Redmond) so I have no problems. It takes me 10 minutes to get to work by car, and about 30-40 by bike. It would take 2.5 to 3 hours on foot, and I'm not sure about the bus.
I have the most fun on my bike, and it means I don't spend extra time at the gym on some cardio machine.