my current job is in downtown Boston, so driving in would be a nightmare. In the two times that I did it for an interview it's usually taken about 45 minutes, if I chose to park my car in the building garage, which charges $35 a day. There's a $10/day lot out in Fort Point, by the State Courthouse, but this would also add at least 15 minutes of walking to the commute.
Public transit was roughly 45m - 1hr. as well depending on luck with bus and T connections.
Door to door, by bike, it's 25 - 30 minutes depending on my luck with the lights. Shower and changes of clothes probably add in another ten minutes.
My previous job was out in the 'burbs' and that was about 1 hour by bike and 30 minutes by car. I'd drive in if I had early meetings at work or some evening commitment at home. Now, it's nice because that excuse is gone.