To work from home it takes longer by bicycle when you factor in the time it takes to cool off and change; maybe 10 - 15 minutes for driving compared to 20 - 25 minutes for cycling.

To home from work it takes less time: 20 - 25 minutes by bicycle again, compared with more like 30 - 45 minutes with lots of sitting in rush hour city traffic for driving. Bicycling home is always more spicy than the other direction: the extra traffic means more cagers blowing through stop signs and expressing antagonism. I've only exchanged words a few times in a year of serious bicycle commuting, and it's always been on the way home.

As others have said, it's totally worth it. I'm moving into my late 20s and I'm in the best shape I've ever been in and I'm actually physically addicted to my daily exercise regimen while so many others that I know struggle to motivate themselves to go the hamster gym.