Scott,
Good comments re: RPTV. I am a former RPTV owner, I owned the Sony KDL-50A2000, a SXRD set from 2006. Based on my experience with it and with my parents' Samsung DLP, I have some observations.
1. Black levels are just not competitive with even average flat panels today. Although some sets have dynamic iris technology, I think there is just too much light scatter within an RPTV cabinet to provide a punchy ANSI contrast ratio that competes with flat panels today. Now, I'm not saying the images look terrible. Not at all. They just don't look as good as, say, flat panels from 2008 on. I was positively shocked when I fired up my 52EX700 for the first time. The black level seemed subjectively at least twice as dark.
2. I personally don't think cabinet size is as big a deal, at least not if you're uninterested in mounting your television. Most microdisplay RPTVs will fit on exactly the same a/v cabinet as a comparably sized flat panel. I know this, having swapped out my 50A2000 for a 52EX700 edge-lit LED set. The only gain for me was space to put a HTPC tower behind the TV.
3. Lamp life and cost is the big bugaboo for microdisplay RPTV, in my book. A UHP lamp will constantly degrade over time, shifting in both absolute brightness and in color temperature. And sure, though I love fiddling with controls quite a bit, I kind of hated having to do it 3 or 4 times during the life of the lamp. Samsung seemed to be trying out LED-based solutions before it exited the market, but it never seemed to go anywhere. But basically, I would not consider a RPTV purchase until and unless the lamp got to a level of providing, say 20,000 hours of use with little to no degradation in performance.
4. So basically, the place I think a large DLP set like the ones Mitsubishi produces can compete is against Front Projection setups. A 90-inch screen for $5k is a compelling value against all the factors that putting together a good FP setup entails. But I would want to see my concerns re: ANSI contrast and lamp life addressed before I'd consider it. Well, that and DLP rainbows, which I can see pretty easily.