I had mentioned this earlier, but my STB ran off DVI-HDMI, after a few weeks of component, and the only difference I noticed was less noise around text, on, say, a sports ticker.
I will re-iterate how much better having one cable instead of five is, especially given how often I unplug my 360 and bring it somewhere with me. I sold my old 360 when I came out west, on the grounds that when I move back east, I would buy a new one with HDMI out. It turns out my timing was perfect. I had saved the HDD from my old 360, so I was able to buy one of the few Arcade bundles left, which are becoming pretty rare.