Just picked up a pair of these myself a few days ago. New to closed backs (new baby in house!) and very, very pleasantly surprised. In the process of comparing them to Beyer DT880s in 250 ohm and my fave HiFiMan HE-6, all through an NJC Reference 2 using the variable gain. Amp is being fed by a Naim CD5XS.
Firstly, i haven't had any fit or comfort issues at all. They slipped on my head right out of the box and instantly felt sealed in the way my IEMs do. I didn't even need to adjust the headband. They are incredibly light and comfortable and the pleather is top notch. More comfortable even than the Beyers - I could definitely wear these for hours at a time. None of "sweaty ears" issues I've read about elsewhere either.
Soundwise, these are still burning in but out of the box I am very impressed. Never owned a full size closed back can before, but I don't hear any drawbacks and the level of isolation is very good indeed, my wife sat next to me on the couch can't hear a thing even though the volume level is slightly higher than I would normally listen at. Bass is very tight and lean but still plentiful, bass lines easy to follow. Superb vocals as well.
Comaprison wise, these blow my old faithful Beyers out of the water, with the added benefit of isolation. Actually a bit saddened by that as the Beyers have been with me a long time
The HiFiMan is a different story. The orthos are in a different league, and at well over 4x the price I should hope so too. Everything is more present, bass is still tight but richer, and so. But, they are heavy and leak like a sieve. I realise it isn't exactly a fair comparison, but the AKGs still give a very good account of themselves and are definitely not 4x worse - diminishing sq returns for cost increase being an unfortunate fact of life in this hobby!
So, as I said, dead impressed by these cans and looking forward to hearing just how much better they can get with burn in.