Um, I walk to work. I live close enough, one mile round trip, that the bike Stuff (helmet, locks, etc.) is just more work than walking.

When I had the job 2 miles away, I rode unless the roads had icy ruts in them or I needed the car after work for some reason. I would guess I rode pretty close to 90% of the time.

DH bike commutes, again, as long as the roads are clear - even on the day after he ran a marathon. He's pretty hard core that way.