Widescreen review did a 2 part story on HDMI cables & there is a difference.
Just because it's digital doesn't mean it's "just 1's & 0's.
Construction, materials & especially the soldiering of connections are important to the quality of the picture.
This picture shows the difference between good & bad cables.
I have some 1M Monoprice cables & they work fine but when I'm putting a 15M HDMI cable behind drywall, it will be a higher end cable like a Kimber Kable, not the cheap stuff!