I just moved from northern Virginia, Arlington. Well, just moved is back in September 99. If I remember rightly, Reston is far enough from the infamous beltway area that home prices and apartment rentals should be "somewhat" reasonable compared to within the beltway. The beltway is loosely defined as the area enclosed by I395 and I495, arteries of I95 that get you around the DC Metropolitan area. In actuality the area immediately srounding the beltway can be rather high priced also. Reston puts you well outside the whole area and most importantly, saves you the horrendous commuter traffic hassles associated with everybody on I95 and I395 and I495 trying to get from home (way outside the beltway where costs are less) to work within the beltway and back each evening. Actually, Reston is one of the places lots of people live who commute into the beltway (primarily government employees).
The possiblilty that so many commuters live in Reston or want to live in Reston may have hiked costs for real estate there exists, but you can still beat the astronomical costs within and around the beltway. If you want to commute - look west of Reston, but not to far, or south or north. Going east gets you toward beltway country. And, by-the-way, your neighbor in Reston is Dulles International Airport.