Ashburn is a very nice area. Lots of amenities. Also, you can find some very good values there. There are quite a few homes that were built a few years ago and purchased at the height of the real estate boom. Some of those are now REOs or pre-foreclosures.
The only real drawback to Ashburn is that it's kind of far away from DC. However, if the new job is going to be around Reston, then that's not a problem at all.
Another great area (just my personal opinion, of course) is around Clifton, Virginia. Check out http://www.cliftonva.us and http://www.cliftonva.org It's a small, quaint town; within a few miles of the town in any direction you can find some really nice homes, good recreational facilities, lots of activities for busy kids, and so on. It's 10-15 miles from Reston.
Hope that helps.