I have a Samsung HLN-507W 50" rear projection DLP. Media is Hi-Def Comcast cable box (DCT5100), soon to be DirecTV HR10-250 (formerly HD-DVR250), aka "HD Tivo". I also have a Bravo D1 DVD player with DVI output. Although not high-def, well mastered DVDs played on a DVI-capable player to an HD display with DVI input can have almost HD quality to the casual observer.
Because of the high resolution, the viewing distance calculation is different from analog NTSC. You basically must sit closer to see all the resolution you paid for. For this reason a physically larger display may be more useful than you first think.
The extreme light weight and relative thin depth of the DLP is nice. The 50" is only 17.5" deep and weighs only 77 lbs. My wife and I have easily moved it several times when re-cabling equipment.
If you're used to time shifting via a VCR, Tivo, or other recorder, be advised HDTV recording is in its infancy, definitely less mature than HDTV displays themselves. Fortunately within the next year HD digital video recorders in cable boxes and satellite receivers will be more available and less buggy than today.
If you don't have HD cable or don't like it, be prepared to put up an antenna. Even if you have an HD satellite dish, you'll usually need an antenna for local HD channels, since the satellite providers don't have HD local channels. See
http://www.antennaweb.org/
Material availability is pretty good, except for the difficulty of recording HD. Many of ABC, NBC and CBS prime time shows are HD. Specials like the Superbowl are HD. HBO and Showtime have HD versions.
Image quality is generally very good, but ultimately limited by source material. There's wide variation in quality of film-to-HD transfers. Likewise the bit rate can vary significantly from some local broadcasters. The worst offenders are those which use "subchannels" to steal bandwidth from the HD channel in order to provide additional lower-res channels like home shopping, etc. The lower data rate can cause pixelation and "macro blocking" on certain scenes.
In general HDTV is now at a maturity level so it's useful, with the caveats of difficulty/complexity of recording and frequent need of an antenna if not using HD cable.
