I started my job on December 2, so I can't speak much of evolution. It's the longest bike commute I've ever had, about 12.5 miles each way. I started riding once a week. Last week, I upped it to twice a week. I'll increase it again soon. When I don't ride, I take the subway. Travel time is the same for both modes, but preparation time is a little longer for the bike.

I sometimes vary my route, but not often, because my main route is almost completely on a bike path. Taking the streets involves dealing with much, much more traffic. The increase involves increased annoyance and travel time. I only hit my brakes three or four times normally, which is amazing for city riding.