I've got a Sony 50" Rear Projection in my living room. Its great as long as :
a. you're a good 6-8 foot from the screen when watching
and
b: you look at it from the same level as it is. Heres a picture on my living room, and you'll see that the screen is low, so when you're on the couch youre looking at it straight on (the taller ones I have seen are not ideal unless you're at the same height)
One problem with them though, is in bright sunlight, they are not so good. The darker the room the better.
However for the money you cant beat them. However, I use a 42" plasma in my office here, and the quality of that is a whole lot better. Worth spending the extra $1000 if you can afford it.