(Copied over from my review on Amazon...)
I can definitely say that this product is not all hype. They sound very good but I can't stress enough the importance of BURN-IN! I have about 200 hours on mine and they are still noticeably progressing to this point.
Build quality wise, these are pretty solid. They aren't the most solid on the market or for the money but they should last. They are a mahogany and aluminum build with a sort of pleather for the pads and headband. Some people complain of sweating ears and that may be true however I haven't gotten to the hot part of our fluctuating temperatures here in Pennsylvania so I can't say for sure. They are very comfortable non the less without any real pressure points. The cord is good but VERY long. You may need to tie to a shorter length when traveling with it. It is 99.9999999% Oxygen Free (Doesn't it seem like they all are?) which I don't think means much but hey, it works. The only downside (sort of) of these headphones is that they are relatively heavy (I'm coming from wooden Grado like magnum V4 headphones which are very light - recommended for open headphones) and don't seem to stay in place when you tilt your head.
These things sound as good as they look and will impress anyone who is a fan of bass. People on head-fi often criticize the bass as being "flabby" and "overly booming". (Thus came the markl mod. If you get them and think that they still have too much bass, I would probably recommend it...) So when I got them and put them on, I was expecting a completely overdone bass sorta along the lines of the Sony "Extra Bass" line (Ughh painful. And I like bass!) but to my pleasant surprise, it was nothing of the sort. I think another reviewer here on Amazon put it perfectly that this a luxurious enveloping bass versus a smash your brains out grrr pain to your ears bass. If you couldn't tell, I love the bass on these.
I am no expert on mids and highs, but all I can say is that these are very pleasant headphones but with burn-in of course. I don't feel that anything is too terribly recessed but they definitely aren't as clear as my previous Magnum V4 headphones. (For those of you who know what they are, that is a no brainer)
Portability wise, these headphones are probably the best sounding portables out there. They do benefit from an amplifier (I have a Little Dot 1+ with mallard tubes and it is highly recommended for budget audiophiles) I have an iPhone 4 and 75%-80% volume gets me to a more than ample listening level. I would recommend getting a case for traveling if you are going to use them for that due to the fact that the mahogany will scratch. (You can find a good case on eBay if you search for "HD800 Case") One thing that I worried about before getting them was if the plug would fit into the case I have on my iPhone. The headphone jack hole on my vapor pro case is 5/16 of an inch wide and it just barely fits into it. So measure your case and if the hole is <=5/16 of an inch, you should be good.
Again, this is a thing of beauty and is meant to be treated that way. The cups will scratch but it does seem avoidable. Just be a little careful and you will get an amazing audio device that will serve you well for a good long time!