I might be imagining things, but it sure looks to me like a lot of the HD800 "haters" have heard the HD800 though significantly worse sources/amplifiers than those used by the HD800 "defenders."
It also seems to me that based on the amount of HD800s you see for sale that a lot of angry HD800 owners spent their hard earned simoleans on the HD800 expecting it to be the be-all-end-all of headphones and pair perfectly with any gear under the sun. I can definitely sympathize with these complaints. At first I ran the HD800 straight from a computer soundcard and I wondered what all the hype was about.
It sure would be great if the HD800 sounded better out of more reasonably priced gear, but, when properly paired with a great amp and source the HD800 is definetly in the discussion for top dog in the headphone pantheon (along with the Stax Omegas and others). If we measure the HD800 by what it is capable of sounding like, then to imply that the HD800 is in any way a failure seems absurd.