I have used HD cable as long as it has been out in this area, not too long ago i got a box with dvi and component hd output. I have a/b compared the video quality of dvi and component watching HD and see no difference. I have a rear projection tv though, and dvi is alleged to make a larger difference on pixel based displays... I have also a/b these at other places on lcd projection and couldnt tell any difference either, but didnt have enough time to emphatically claim that dvi was no better.

Further, I have used/demoed "upconverting" dvi output dvd players and when compared to component, I always saw component as being better.

Right now I am using DVI from the cable box and component from my dvd. Mostly because using DVI frees up another component input on my tv.

I have top of the line monster cable.

Interestingly I also have the top of the line monster "hd" s-video that I use when watching regular tv from the hd box, and when I watch hd through the s-video the quality is 95% as good, except if the images are moving quickly or viewing something like grass.