I had a poor reaction to a pair of HD800s I recently bought.
Background... I damaged my ears about 12 years ago testing some tweeters in a DIY speaker project. I have had a low level ringing in my ears at around 7500 Hz since then.
In burning in the HD800s, I used my Centrance HiFi M8, as well as a Meridian Explorer/EL84 tube amp. The harshness of the HD800s diminished at about 80 hours (worst was the tambourine on "High Life" from Jazz at the Pawnshop).
I have enjoyed my LCD-2F for a year now, with no exacerbation of my tinnitus.
Doing A/B testing of the HD800s against my LCD-2F, after a few listening hours the ringing in my ears got worse and I developed a low level headache each time I tried the HD800. After 100 hours of burn-in, I returned the HD800s. However a week later the increased ringing remains. Now I listen to my headphones at very low volumes, and hope the tinnitus diminishes again.