Yes, cables differ considerably in parameters that affect performance, including impedance consistency, skew, cross talk, etc.. The point is, though, that as long as the received signal is close enough to the transmitted signal, no data is lost. If data is lost, because of the encoding method used for HDMI, you get one or more pixels that are just wrong. If you get a few of them, you see sparkles. More, lines of sparkles. Enough, no picture. What you don't get is the kind of effects that you can get with analog signals, like differences in hue, contrast, sharpness, etc. And even with the worst, cheapest HDMI cable, if the received signal is just good enough, no data is lost and the picture will be identical to that produced by the best, most expensive HDMI cable. If you don't understand that, then you don't understand a thing about HDMI.
One could argue about HDMI audio being less than ideal. But that is due to how it is encoded on the same TMDS pairs that transmit the video than differences in HDMI cables. The same thing holds as for video. If the signal is just good enough, no data is lost.
Now, if you were an early adopter of monoprice's Redmere cables, it is possible that the cables you had were indeed crap. Monoprice acknowledged that they had a problem with some and offered to replace them. That doesn't mean that all cables incorporating Redmere technology are crap, or for that matter that the current monprice products incorporating Redmere technology are crap.
Edited by Colm - 11/28/12 at 11:17pm