I have the Sony KP-57WS520 which does have HDMI. However, there is no difference in picture quality between HDMI and component on this display once both are equally calibrated. In fact, component *might* even be a hair better in terms of sharpness/contrast - but it's very, very slight and hardly noticable.
I just bought a PS3 today and will try out component and HDMI tonight just to see how component is implemented, but I bet they'll be virtually identical. In fact, the clipping issues of the PS3 only occur with HDMI as far as I know, so might just use component myself. I'll post comments later. Looking forward to see how well the 480p output is for SD DVDs, as well.