I take them every where, if I don't want to drive....Nicer Drivers and Cheaper, with less wait time than Taxi or Shuttles....
Should be interesting to see if hotels closest to the new Silver Line Metro stops now become Provider top picks in the area.
Certainly opens up a whole new market for those of us unwilling to drive out to Tysons due to traffic headaches.
I plan on adding Reston and Herndon to my schedule at least twice a month. 
While the metro may stop there, scouting it out it seems like its still a bit of a hike to even the closest hotels
or the providers, they can take the metro to Whiele (however it's spelled, it's early and haven't had my coffee yet), and then hop in a cab and take a short inexpensive cab ride to a hotel.
Oh yeah forgot about that. If you are in Tyson's and taking metro in for example, just about every hotel has free shuttle service. A lot of the hotels in the Herndon/Dulles area already offer shuttle service too and from the airports. Metros will be next for sure once it's all completed.
I take them every where, if I don't want to drive....Nicer Drivers and Cheaper, with less wait time than Taxi or Shuttles....
....when i'm not and want to shop out there i'm happy it'll be a bit less of a pain to do so for sure. *as someone who normally gets around without a car because I never learned to drive lol*
though only one real option in the larger Tyson's area.