The three stops so far:
Green Turtle Ballston
Green Turtle Dulles Town Center
Velocity 5 Centreville
I suspect they will have separate buses for each stop. And you won't have to tip, I bet.
Cost would have to be competitive with Metro but I would pay a bit more for the convenience.
It's great that they are getting this going, but are these the only options for the forseeable future? They're all in the Western direction, how about South, or North into MD?