On Friday I had a 5 minute walk to the bus stop in Gaithersburg. The bus took me right to the Southwest ticketing area at BWI. I flew through TSA-pre security, and at the other end hopped right on the bus at DIA and was dropped off with a 5 minute walk from my apartment.
I left Gaithersburg at 4 pm and arrived in Boulder at 9:45 pm. I blogged and tweeted the whole flight and both bus rides. Total cost : $17 in bus fares and $130 for the airline ticket. No parking costs, no rental car, no dealing with Friday rush hour traffic.