Projector technology has improved 100x over the past 8-10 years, and average lamp life is between 2000-4000 hours now. Something to consider is how much brightness is in your home theater room already (from windows or lights). Ever been in a movie theater when someone opened a door that leads to outside? Same "Dark is better" rule applies to HT projectors.
My main TV is a projector setup (Infocus IN76 720P). Obviously, you cannot touch the size with any other technology. When I bought my projector about three years ago, I paid about $2300 for it, and another $700 or so for the screen.
At that time, it was hard to by a 50" HD set for under $2000, and most mid range (not high end) 55"-60" HD RPTV's were $3,000 plus.
I paid $3,000 for a 118" HD setup. Granted, I have to replace the bulb more often then an RPTV, but if I had gone with a decent 60"+ set at that time, it would have cost well more than I paid, and be tiny in comparison.