If you'd like an option for your flat screen besides mounting directly onto the wall, check out this piece specificially made for flat TVs. We saw this one over on Freshome, and then saw another similar option over at Pottery Barn in their recent catalog.
This modern version, by Futura, retails for a very reasonable $599, and is on casters, so it could be moved quite easily if need be. It holds TVs up to 42" in size. The Pottery Barn model is $1,499, but may fit your decor better than the modern version might. It also has 2 more shelves on each of the side storage areas as it is 14" taller than the Futura model.