If I optimize my settings for component and then compare component to HDMI, then the component picture is much better. The HDMI picture looks washed out with terrible blacks.
If I optimize my settings to HDMI and then compare component to HDMI, then the HDMI picture is much better. The component picture has terrible black crush and colors are muted.
If I compare the optimized component picture to the optimized HDMI picture, then there is a slight edge to HDMI. It is a bit sharper, the blacks a bit better, and the colors a bit more vibrant. The component picture is very good on good sources, but I'd say that overall, it is about 95% as good as HDMI on my set.
This is using a Panasonic CRT-RP HDTV and a 622 receiver, using both E* HD and OTA HD channels. It is also using pretty good quality component video cables, from AudioQuest, vs an $8 HDMI cable from monoprice.