When I first starting work for public transit, I actually still took my car quite a bit, because the closest bus stop to me was about 3/4 mile, and there was a pretty steep hill included in that. Plus it was a route along a main road, which meant lots of stops. Took about 20 minutes, AFTER the walk to the stop for a commute I could drive in about 7 minutes.
But a couple of years ago we started a new neighborhood route. The stop is just about two houses away from me. And because I'm really at the beginning (or end, depending on which way you're headed) of the route, and most of the riders live further out, there are usually very few passengers, if any at all, between my stop and the transit center, so the whole trip takes at most a couple of minutes longer than if I drove. BUT, really, it's faster, because if I drive, I have to park in the garage across the street then walk in. The bus takes me right up to the platform, I hop off walk across the platform (which only employees can do), in through the second-floor door and I'm about 15 feet from my office.
Oh, and then there's the fact that, since I'm an employee, the ride is also free.
The only reason I drive to work now is if I have plans for after work that I can't get to on the bus.