To address your question about HD-DVD (without getting into the format war/DRM issues), yes, HD-DVD will look better than DVD on a 720p screen. DVD's resolution is 480p maximum (sans upscaling). HD-DVD will do 1080p, but afaik, it will also do 720p just fine. In any case, I'd rather remove pixels than add them--you're going to get a better picture that way.

I am the Doctor, and THIS... is my SPOON!