I've been bouncing around this question also, but I've decided(?) to go FP - eventually. My main factors are:
Don't need a tuner - digital cable box outputs composite video (ick - but...).
Don't need speakers/audio - use SS receiver.
Can't get huge 300lb box down the basement stairs!
What still bugs me is that RPTVs are cheaper, even with the stuff I don't need! It SEEMS POSSIBLE that prices will come down later this year, so I wait and scheme...
I borrowed a DLP (NEC LT81) from work and was pleasantly surprised at the image - just no shadow detail, so contrast range is VERY important (get 400:1 at least). One factor that I really liked is that (when proj on the wall) you get a good image from anywhere - with all RPTVs there is a limited horizontal AND vertical "sweet spot" for a clear view; they have lensatic screens to boost the CRT output. I think this far outweighs the "dark room" limitation. The NEC only had 800 lumen rating, but it seemed very bright; 1000+ would probably allow some room lighting for casual viewing. Most of the *cough*film enthusiasts*cough* here may be too extreme in their image/lighting requirements. Using my off-white painted (Behrs "Swiss Coffee") wall worked great - it's flat, smooth, and free. OF COURSE, AN EXPENSIVE SCREEN WILL IMPROVE YOUR IMAGE (did they hear that?)
Final advantage? Next time my wife wants to rearrange the viewing room, I could pick up the projector and move it myself! Try that with a 65" RPTV.