Dr. Gridlock article from the Post (http://voices.washingtonpost.com/getthere/2010/06/loudoun-tysons_express_bus_to.html), plus GGW post (http://greatergreaterwashington.org/post.cgi?id=6043) with commentary.
Service starts June 21st with 7 round trips a day between Leesburg and Tysons. In a time where transit costs seem to be spiraling out of control, this turns out to be one of the biggest bargains: $3 one-way (this when combined Greenway + Toll Road tolls during rush hours are near double that).
You are quite correct, the fare is quite a bargain. Fairfax Connector charges $7.00 premium one-way fare for rush hour express service between Reston and Crystal City (a much shorter distance than the Loudoun County service travels).