I have some of the Vortex Viper 10x32 binos. I'm not sure how much the HD versions are, but based on some other HD optics I have, there could be a noticeable improvement. Did you happen to compare the HD with the previous non-HD version on a side-by-side basis? I'm curious as to the differences. I do know that when bigger glass, like the lenses in my Swarovski STS-80 HD spotting scope, is used, the chromatic aberration at the fringes of the field of view is significantly diminished, and the image is easier to resolve due to sharper color edging.
I have found the Vortex binoculars to be very good, but not quite in the same category as the far more expensive Swarovski and Leica optics. To some extent we still do get what we pay for, but the very small additional gains over the Vipers costs several multiples in the purchase price. The Vipers provide a lot of quality at a reasonable price, for sure.
Allan