I've made some SD vs HD resolution comparison on my 26 inch Sammy HDTV. The difference is quite impressive - this TV deserves it's price tag and worth every penny. Can't wait for new HD-DVD and Blue-ray players and beginning of digital HD broadcasting in Russia/Europe.
So... take a look at these pictures I captured with
480i composite,
640x480 VGA (~480p) and
1280x720 VGA (720p).
Now it's time to make your own decisions. Good luck!