I do my 19 mile commute in 1:15 on decent days, and 1:10 is my best time. That being said, it's now at a point where I'm leaving at dawn and getting home at dusk. In 2 or 3 weeks it'll be fully dark on at least one end of the commute. I'll probably have to stop after the DST switch at the end of the month.

If you're really committed you can get a good light or two and just ride in the dark. My office is closing after thanksgiving though, so my commuting days are over after that, so I personally don't have a good reason to buy an expensive light.