I have recently added an HD LED TV in my library with both a composite cable (from an Elan 8.6) and an HDMI cable (from a Denon AVR-5308CI). Oddly enough, the composite seems to handle HD just fine. For some material, it is almost more pleasing to the eye than the HDMI output from the BluRay player. Yes, I can apreciate that the HDMI is technically superior and has more detail, but sometimes the detail is subjectively less attractive to the eye (or maybe that it is MORE attractive and therefore distracting). This has been the opinion of several persons who have seen an A/B test.
The new TV is about 45' from the AV equipment but the cables (from Blue Jeans cable) seem to perform well at a distance (I also ran some tests with the TV is the same room with shorter cables with the same results).
Now, I realize that composite standards have much lower bandwith and that there can be issues with dot crawl, etc., but I am hard pressed to understand what allows me to get an excellent 16:9 high def. picture from a cable that almost everyone universally says cannot carry HD. Is it the cables? It can't be the Denon because I get similar results from the BluRay or STB running directly to the Elan.