Good points everyone.
There's obviously room in this HT universe for both flat screen displays and projector / screen systems - with a variety of technologies for each and every component to choose from. Meaning that we should all be able to find something with good image quality, at a good price, that suits the room it's intended for.
Most of us don't have the space, nor budget, to do the ne plus ultra of systems, but with the exception of one friend who insists on running his flat screen with all the "special effects" (240Hz, frame interpolation, etc. etc.) fully engaged (resulting in the most unreal-looking artificial video-like image possible) none of the HT's that I've ever visited ever presented a video image that wasn't perfectly good to watch without detracting from the source material.
I like my plain-Jane Sharp Aquos 56" 1080p LCD in the ambient light-infused family room HT. Until it fails I see no need to ever change it.
I really like having a screen / projector system in my main HT, where I can control ambient light down to basically none at any time of the day. I like that I invested a lot in the screen (back when I had the money to do so) and that it should last a lifetime. It's only 96" but I sit only 7' back from it. As I've pointed out before, I designed it that way to mimic the (visual) experience of sitting half way back in a big movie theatre watching a big screen. And as I've preached on many occasion, I really like that it is acoustically transparent thus allowing for as close to ideal speaker placement as you'll likely ever find in any HT.
The only "picture" component that I'd thus consider replacing in either HT, would be the main HT's projector. However with replacement bulbs now costing all of $60, and me still loving the picture that that TI DC3-based 720p DLP puts out, I'm in no rush - unless it craps-out altogether. (The original colour flywheel suffered an infant-mortality and was replaced under warranty, but there's been no issues since.) Besides, at some point I would expect my visual acuity to start degrading with increasing age to the point where I won't likely be able to fully-appreciated ever-increasing improvements in the technology.
Jeff