Today it's easy to look at commuting by bike (or any other human powered way) as a way to save money with gas getting awfully close to $4 a gallon. But it is also a great way to get in a workout for those who have very busy lives.
I look at my commute as an easy way to get in at least an hour of total bike time a day, and that hour comes at a cost of only about a half hour (if i drove it takes 15 minutes each way). Add to that that it's much easier to ride for an "extra" half hour or so on the ride home and actually pick up an hour and a half of riding each day. This has been a great way to try and sneak in bike time when everything else in your life seems so scheduled.