I too have had mixed results with HDMI. I have a Vizio 50" plasma that has two each of HDMI, Compontent, S, etc. I also have a Pioneer A/V with all of these as well. I have DirecTV's HD H20 which has HDMI and Component for video.
HDMI from the H20 to the plasma was great. It was also good via the Pioneer but whenever I changed input sources, the H20 would go bananas, endlessly rebooting.
HDMI from the Pioneer to the plasma seems to be great no matter what the input source is on the A/V. But to avoid the H20 problem, I run Component to the Pioneer which routes it to the plasma via HDMI.
I just returned an Oppo 'up-converting' DVD player. It has a DVI output which is compatable with HDMI but doesn't include the audio. Oppo to Pioneer via DVI->HDMI worked but the Pioneer expected there to be audio on the HDMI input and ignored everything else, including the optical I tried to use. Component worked but then I don't get the Oppo up-conversion feature.
So I tried DVI-to-HDMI directly to the plasma and got little specs like snow on any of the up-converted formats (720p or 1080i). After several cables and swapping connections I gave up.
Kinda long, I know, but for me HDMI is a mixed bag and I have yet to be disappointed with component picture quality.
-Brian n8wrl
