I live in Seattle, WA, am 43 years old, and have been commuting by bicycle for the last month, and am enjoying it very much. I ride just a little over 5 1/2 miles each way, for 11 miles a day 4 - 5 days a week. I find it the one form of regular exercise that I really enjoy and can keep at (so far).
I'm riding a 20 year old Univega 12 speed, and would like a newer bike, but will wait until I know more what I want and until I can afford what I want.
I've been reading the bike forums here and am finding them very helpful.