It depends on the equipment (TV) you are using. If you use a DLP or simular tv (Digital) it will improve the picture , but if you have a CRT based tv you will not really notice any change because there has to be a analog to digital conversion in the chain somewhere. DVI is not really intended on improving Picture Quality it is designed mostly for copywrite protection.
For my setup, 811 > DLP projector, I have both hooked up also. With the DVI cable I see a picture that looks like the 'sharpness' is turned up. Grainy is not the word I want to use. Looks smoother with the component.
I still haven't figured out which I like better. For the SuperBowl I ended up watching with the component. But for Discovery HD Theater programming, scenery etc, I have been using the DVI.
Before the projector I had a Toshiba 65" RPTV and I didn't notice any difference between the DVI and component.
On my Samsung HLN507W DLP, DVI delivers defintely better sharpness on native HD content.
You can find lots of 6' DVI cables on e-bay for less than $10.00 shipped. You do not need to spend big $$$ on DVI cables, especially if you don't need one over 6' long.
If your set is a native digital one (DLP, Plasma or LCD), for under $10, why not order one and experiment?
Thanks for all the responces. My TV is a Rear Projection Mitsubishi 55". I will go and get a cheap cable and try it out even though it sounds like it will not do much since it is a Rear Projection. Thanks again..
I get a better SD picture with DVI. Don't notice any differenct on HD. I have aan Hitachi 57S700 RPTV. Component on SD is dark like the S-Video problem.