Build - 
 
These are very high quality feeling headphones. The metal headband clamps enough for a decent seal, but not enough to make them uncomfortable at all. The metal attaching the cups to the headband is very rigid, and the plastic cups feel super solid. No complaints about the cable either. No fear of these breaking any time soon.
 
The isolation is quite good. They have trouble blocking out low bassy sounds, like a bus engine for example, but I think that's a common problem in most closed headphones. 
 
Comfort -
 
Easily the most comfortable headphone I've ever worn, by far. I wear these for 6+ hours per day with no issues. The padded headband, the plush velour pads, the perfect clamping force, they're like having pillows on your ears.
 
Sound -
 
The bass extends very far, and the impact is incredible. Pretty similar to the ATH-M50s bass. Songs like Ratatat's "Eight" sound amazing on these.
 
The mids are a tad recessed, but full sounding, and very detailed. Not much else to say about them.
 
The highs are present, but rolled off and put a bit in the background on many tracks, in my opinion. They lack the sparkle and detail of something like a Shure SRH940. I EQ'd mine up by about 4db at ~3-6KHz and 14KHz which gives them a bit lighter feeling.
 
The soundstage is decent for a closed can at this price range, but I find that, especially with symphonic metal, they lack the depth and layering required and everything gets mushed together. Quite accurate though, which makes these a good can for FPS gaming. Very easy to tell what direction things are coming from.
 
 
Conclusion -
 
An excellent headphone, especially for electronica, but sounds good in almost every genre (I'd say every genre but I don't listen to them all). Definitely worth the ~$200 street price.

A friend picked up the ATH-M50s as his first decent headphone, and we spent a couple of days swapping back and forth between them and my DT770 Pro 80ohm.
 
- Build
 
I found the M50s to be quite well built considering how much plastic was on them. They felt solid, and the folding mechanisms were smooth and felt quite good.
 
The pads were very soft, and the pleather felt rather nice and sealed very well. The headband, however, was not padded very well, and along with the high clamping force of the M50s, lead to comfort issues.
 
- Sound
 
I would describe the M50s as having a very V-shaped sound signature.
 
The bass extension, quality and quantity easily competes with my DT770s (although this could be because the M50s seal better, I think if I put (p)leather pads on my Beyers they would get a fairly significant bass increase).
 
The mids are quite recessed, and maybe a bit thin sounding. Very detailed though, when not overshadowed by the other two ends of the spectrum.
 
The highs are what ruined this headphone for me. Listening to Pendulum's "Showdown", the cymbals in the first 30 seconds as well as any S sound from the singer made me cringe. They came off as very harsh, especially in combination with the lack of mids. I may just be more susceptible to highs than most people, but I really couldn't enjoy much of my electronica or any music with a lot of high frequencies without a pretty significant EQ.
 
 
- Conclusion
 
After a week, my friend brought the M50s back and got some DT770 Pro 250ohm instead, which we both preferred much more. These could be decent headphone for around $100-$120, especially in regards to build quality, but certainly not for their current price of ~$150, in my opinion.