Meh. Flying into Baltimore is usually cheaper anyway, and DC area public transit is fantastic. (Well, compared to Ohio.)
If you're flying from Ohio, it will probably take you longer to get from BWI to your destination in DC than from Ohio to BWI.
And then we can lament the often crappy service together.
(Note: I am a huge fan of public transit, so that's not a general bash. DC's sucks unless both ends of your trip are within walking distance of a subway station.)
As it turns out, we had a trolley-based mass transit system until GM and Ford (and Exxon?) bought it up and dismantled it. (No joke.)
When I lived in Sterling, it was a 15-minute drive to Dulles. When I moved to Silver Spring, it was a 45-minute drive.
From Sterling, there were no mass transit options whatsoever, AFAIK. Of course, with a 15-minute trip, there's really not much incentive to look for alternatives.
From Silver Spring, you CAN get to Dulles via mass transit... I had to walk to a bus stop, take the red line downtown, change to the orange line out to West Falls Church, and take a Washington Flyer to the airport: 2.5 hours.
So I agree... worthless.
I also found that biking from Silver Spring to Crystal City took approximately the same amount of time as the bus/metro combination, and had fewer delays.
Would you believe, btw, that Seattle's equivalent to the Metropass has a 24-hour latency? So if you put money on it, you have to wait for 24 hours before you can use it?