I designed the AV room of my dreams, completed in 2010. My front room, 13ft x 15ft, had always been my two channel listening room and sounded excellent. But I got into home theater/projection big time and totally reno'd the room to have a 4 way automated masking screen, hidden projector, sound treatment "built in" to the design, custom made furniture precisely to my demands of comfort and aesthetics, etc. It turned out even better than I dreamed and has been the best AV thing I've ever done.
My one single problem is that it's the only room I have for all my hobbies. So my two channel speakers (Thiels) share room with the surround speaker set up. The way I had to set up the room means the two channel speakers have to sit out in the room, one right near the room entrance. On the positive side, the room has never sounded better and even big speakers like my Thiel 3.7s sound unbelievable.
But for aesthetic and ergonomic reasons, my big Thiel 3.7s are a bit of a problem and I have to downsize a bit. So that's a bit of a bummer.
Though it looks like I'll be good with the slightly smaller 2.7s (or something else) and subs.
But beyond that it's a dream room and every time I use it I feel like pinching myself with glee.