Is a DVD player that upconverts (scales) the encoded 480p signal to 720p or 1080i really worth it? Current fixed pixel displays (usually 720p) need to do the same conversion on all incomming signals anyway.... It appears to me that these new 'HD' DVD players are just a gimmick. They really don't send an HD signal, they just scale it. (You can't create information that was never there to begin with).
I have a Toshiba SD-5970 that upscales to 720p and runs to my JVC 52" DiLA via HDMI cable. The over PQ is noticable better when compared to the same signal over the component cables. The biggest difference is due mainly to the pure digital signal. There is less graininess, less line flicker, and an overall more stable, smooth picture.
If you use component, the DVD player converts the signal from Digital to analog, then the TV converts the analog signal back to digital. The upscaling DVD players do the upscale conversion in the digital field, sends the signal to the TV in digital, and the TV does not need to convert anything, just display it. Less steps, less chance for "noise" or any other problems that might occur.