I started July 1 last year, parking 3 miles away, and doing it ~3 times a week. Rode only a couple times in October, then quit until this month, as I wasn't set up (mentally, and bike-wise) for cold/dark riding last year.

This year, already up 7-9 miles each way, and hope to invest in some fenders and better lights to increase the number of days that I commute. I did buy some street tires for my hybrid, hoping that will make the ride a bit faster/cooler.

Traffic is so bad on the beltway around Boston, that it doesn't take me much longer to bike than drive. It adds about 45-60 minutes to my day, but I have more energy in the evening than when I wasn't exercising.