This room used to serve as a two channel listening room in the basement but we found that we weren't going down there to listen much so the stereo went upstairs.
I stumbled upon a CRT projector about 6 years ago and have been slowly assembling a decent theater around it. So far I haven't seen a digital that matches the picture quality of the CRT HOWEVER I haven't seen them all. I'm sure in the next year or two the CRT will be surpassed.
This projector is mounted in a hush box (necessary) which is vented out through the joists via a fan box in the adjacent furnace/laundry room.
The screen is a home built "torus" screen which works quite well and is a fair bit brighter and punchier than the typical flat screen with gain. It's a bit of a pain to build though.
The thing that really needs upgrading is the sound system. Although the NHT's are adequate I would prefer something a little more dynamic. The fact that all of the front speakers sit behind a false "grillcloth" wall, speaker selection gets a tougher as I can't have a rear ported unit. I would really like to use active components here such as Dynaudio pro monitors or PMC AML1's. The active speakers are great in these instances as you can generally tailor their sound to the room and provide a bit of treble gain to compensate for the cloth in front of them. It also helps that they are front ported.
The HTPC works well but I will soon be looking into HD-DVD or BlueRay sources as the HD format is simply stunning on an 8' wide screen.
This theater project has been a lot of fun, was assembled for less than the price of my turntable and probably used equally as much or more. No diminishing returns here...