- It's faster than any other mode of transit.
- It's completely predictable. My ~3 mile commute takes 13 minutes +-1.
- The bike leaves exactly when I want it to. No waiting, no delays, no announcements about sick passengers, police actions, or signal malfunctions.
- No going underground to the train platform to wait some indeterminate amount of time, especially in the summer, when the temp. can hit 120 degrees, and the station becomes the very vision of hell.
- The bike can get through almost any traffic.
- You actually see and experience the world, the environment, sun, sky, the weather. You don't go down into a hole in the ground, wait a while, and emerge from another hole in the ground. Not strictly on my commute, but I've seen far more of the city by bike than I ever did traveling by train.
- No jostling with other grumpy, harried, bored passengers, squeezing into overcrowded cars, listening to crazy people, preachers, the spiel of panhandlers, or other loud, obnoxious people.
- It saves on train fare.
- It's fun.
In some ways, I actually love the subway, but all in all, I don't miss it.