I know a few high-end AV guys. They all say don't put an LCD flat screen over a fireplace because heat affects performance and longevity. Didn't ask about the soot.

we've had 48" LCD flat screen on our fireplace mantle of our woodburning fireplace for several years. So far, we've had no issues at all and absolutely love it our den is about 18' x 20'. We never thought to consult anyone about it, just went to Best Buy and bought the t.v...they only had one that's base would fit on the mantle..no complaints or problems here.

I've got a 42" plasma above my fireplace. At first, I didn't enjoy looking upward at the TV, but I kept it there because the position makes viewing from my dining area possible. Now, the upward viewing angle is not bothersome.

Thanks for all your replies. We are mostly going to go with this idea. Our mantle is pretty high, so we tried getting estimates to lower it (cut out a portion of the surround), but it seems pretty expensive to do that and since this is a brand new house, we are not sure if we want to start breaking things.

We put our LCD above the fireplace five years ago and it is a total non-issue. We did have a mantle which acted as a bit of a break for the heat.

We also used a mount that tilted down a bit, which was nice. No one ever complained.

Since your house is new, you should check the specs of your fireplace and look specifically at the CLEARANCES. These numbers refer to the distance around the firebox that needs to have only noncombustible material, like marble, slate, metal, etc. If your mantel is wood and your fireplace was installed properly, you can be sure that placing something above the mantel will not be a fire hazard. But heat rises and therefore the wall above the firebox will be warmer than, say, another wall in the room. There is therefore a risk that the extra heat will shorten the life of the TV.

We have a Samsung flat screen LCD and in very fine print it is stated that the warranty is void if hung over a heat source.