Brett, do you have the HDMI cable. If so, how would you compare it to the standard blue/green/red video cables?
I recently upgraded from monster component cables to HDMI. I have seen the most improvement on my regular (non HDTV) digital cable programs. HD is already fantastic even with just the component cables, you won't see much if any upgrade with HDMI.
However, I have noticed that my gaming experience with the Playstation 3 and the XBOX 360 is much better with HDMI connections.