HDCP stands for High-bandwidth Digital Content Protection. It's a digital tag that is added to HDTV programming to prevent downloading on the internet. It's to prevent what happened to music industry, for the movie industry. It' also a flawed product by Intel Corp. that should never been allowed, but with the FCC, money talks...
If your set dosen't have HDCP compliancy and DVI, all you're gonna get is standard-def, or 480p images when trying to watch HDTV programming with HDCP.
Plasma TVs are better than LCDs, for TV viewing, but LCD TVs are getting a lot better, and they are a lot better than they were when I was looking for a HDTV set. True, they need to be "recharged" when they get used up, but the truth to that has really been blown out of proportion.