I've got the original Xbox 360 (not the Elite) so I don't have an HDMI port on it. I'd upgrade to the Elite (maybe) except it would bring on the whole DRM problem all over again because I'd be switching consoles. No good.
Turns out Mad Catz released an HDMI conversion kit for Xbox 360 so you can just buy this adapter and still get the full 1080p goodness you'd get from the Elite.
I saw this bad boy the other day in the Buy More and thought it looked interesting, so I mentioned it to my dad, who is also interested in stuff like this. It's $90 so it's a little more expensive than an impulse buy.
Dad promptly went out and bought it and says it is awesome. He says he and my mom both can see a very obvious visual difference from using the VGA cable and that it's so clear it almost hurts.
Obviously, your mileage may vary, but I think I'm putting this on my list of things to get.