Post on a PS3 board about HDMI and an answer to the question of the difference between a $10 HDMI cable and a $150 HDMI cable. This post from someone who claims to "live and breath digital and analog signals every day" to help people understand HDMI cables.
That answer is, "No, an expensive HDMI cable will make NO difference in the quality of your picture OR sound"
I'm sure the audiophiles will be up in arms about it, but that is probably just because they feel silly for paying $150 for cables and their $20 diamond studded connectors :)