HDMI works fine with my Samsung TV, although I've read accounts similar to what the other poster mentioned above, ie that on some TVs there is an order of turning things on to get it recognized, like perhaps having to boot up the TV while connected. But my Samsung didn't require that.
Only problem I've had, is that my Diamond seems to overscan or something via HDMI, ie I'm missing an inch or two of the screen on each side. Doesn't happen with my other HD sources. I haven't tried it via component yet, to see if it does the same thing there.
EDIT: Slightly related, I recently observed that when I disconnected one of my receiver's HDMI cable (I think... might have been component, but I don't think so), that my TV still recognized that the cable was connected. Ie usually when I remove a source, it dissappears from the sources that you toggle through when you change sources, but I had this HDMI2 source showing up when nothing was connected to the cable. When I pulled the cable out of the TV, then it stopped recognizing the input. So I guess that HDMI has some completed circuits that tell the TV that something is there.