I've been surfing through more stuff on AVS Forum, and they seem to be saying that the quality jump when you go to DVI is worth the bother. Here's an AVS Forum thread and here a FAQ on DVI, HDCP, and HDMI.

In short, if you buy the pricier TV set with the DVI and buy a suitably equipped DVD player, you'll start seeing significant improvements in video quality, right off the bat. (Or, so they claim.)