I have stayed at the Hyatt Reston 3 times this year (2009) and I would highly recommend it. The hotel is a high quality, well maintained, and has an excellent location - sits in Reston Town Center.
The rooms I have stayed were a good size and very clean. There is a decently equipped exercise room and a pool. The resturant in the hotel was excellent and if you want something else there is a Panera Bread in the same building. Within a 2 block radius there is a Mortons, COSI, S&M, Jacksons and others I can' remember the names: Mexican, Italian, and others + a Starbucks. Also if you have kids there is a movie theater about 100 yards from the hotel.
If you are in Reston on business or pleasure you won't need a car to get around if you stay at the Hyatt since all you could want is almost next door.