Ok when it comes to HDMI the goal was to always have good quality. The difference between an analog and digital is that digital ENCODES the information, it either gets there or not. The only thing the cable gives you is bandwidth.

Analog is different. The signal is itself the image, so a poor signal = poor image.

MAYBE if you have a projector projecting onto a movie theater screen will a better HDMI cable matter... maybe? because of bandwidth limitations if the sender is smart enough it might send info at a lower resolution. Other than that I can't see theoretically why a good HDMI cable will help.

Also on my 42'' tv, I've yet to be shown a performance improvement when connecting my XBOX 360 via component or hdmi. It looks identical. And if HDMI is better than component, then I don't see a reason why you would ever need a good HDMI cable unless you are a movie theater and the theoretical problem does exist.

Edit regarding bit errors... Lets assume that the cable you bought is a good quality cable. By good quality I mean most seem to be shielded and not cut and no shorts. This is a reasonable expectation. I've yet to see an argument for buying more expensive super gold plated uber network cables. Hey why is your network cable that handles SO MUCH DATA not gold plated shielded etc.?