I bought and have been using these headphones relatively consistently for the last four months, and for the life of me I cannot understand why these things are so praised. They sound... okay, but not really anything I would go over the moon for. I own a decent assortment of other headphones, and most of them range from moderately superior to these (Audio Technica M50Xs and WS1100is, BeyerDynamics's DT990) in terms of an overall enjoyable listening experience, to simply blowing these out of the water (the HD6XXs). I realize the enjoyable listening experience is completely subjective, so to other ears these may sound vastly superior to the other headphones I've mentioned, but I've tried these things through DACs, through Amps, and I just don't hear anything that warrants the rave reviews these headphones receive.
On top of that, they're not very comfortable. They're a bit on the heavy side, with a fair amount of clamping pressure. And while it might be due to my freakishly large head, but the headband will usually press down on my head after wearing these for a while. Finally, the sound leakage on these things is I N S A N E. The sound these project out the back is so loud that it's only a touch louder to me once they're actually on my head! I realize that sound leakage is inevitable for any form of open-design headphones, but I own several other sets of open-back headphones, and the sound leakage doesn't come anywhere near close to these.
I'm not trying to take anything away from the people that love these headphones, and if the reviews are anything to go by, I'm certainly in the minority. If anything, I'm glad so many people are able to enjoy a listening experience from these that I apparently can't, but I had to offer my opinion, especially when I hear these frequently compared to the Sennheiser HD6XX, and in my opinion it's not even remotely close. If you enjoy these then that's great, but I just cannot seem to get what people are loving so much about these.