I'd love to be able to mount my TV over the fireplace. If you're concerned about the height, they sell movable mounts that let you pull the screen down (of course, you have to be concerned about heat).
Most fireplaces (and their surrounds) are way too big. Our surrounds are huge. They're made as statement pieces. I'd rather have a smaller surround and a TV over it.
Personally, I think fireplaces are just energy-sucking holes in your building's exterior, but everyone seems to want one. Watch home shows where the people specifically look for fireplaces...in Texas. Uh, you're in freaking Texas! You'll use that fireplace on that one "cold" night in January.