When I heard them first, I was dejected and fuming at my decision, Now, After apprx. 50 Hours of burn in , I thank my self that i didn't return them back.
 
Let's start with the outside first-
 
Looks- Now, I don't know why some people describe them as plain-jane looking or being too introvert/somber . I got my hands on the Limited edition and let me tell you, They are as outwards as any others, having said that, They still maintain a non flashy demeanor (Unlike Beats). The limited edition beautifly franksteins an unique combination of Silvery white with a hint of  blue tint making them attractive and fresh.
 

For a serious music lover, They should match his choice. Unless you want a 300$ necklace, I personally find them really  good and sporty.
 
Durability- Now, if you are thinking of portable use this would come to your mind and let me tell you, These are really Panther Tanks(Used by Germany in WWII), Strong, Robust and Trustworthy. Will survive much more than a fall. Feel free to carry them even in Afghanistan.
 
Comfort- Yeah, They are not your pillow on which you could go for a nap, To be fair, they do need some time to get used do, The earpads are pleathered, which is plastic+leather, (for 150$ they really can't give you real leather), Thus turning them surprisingly hot after long continuous use. The clamping force is another issue to take care of, I advice you to stretch them according to your head size and comfort, once done, They are good to go, Regarding the earcups- They are a cons. of closed/sealed headphone, so be prepared to sacrifice some comfort for isolation and portability.
 
Portability and isolation- They are not as portable as a Sennheiser PX100/200, They do fold but not as much to be treated as purely portable cans, However, If you can manage the cord and get comfortable with the headband/earpad , they can be portable,. They swivel and fold well small enough to be kept in the pouch/bag. This makes them multifunctional. They are pretty light as well for a full sized headphone.
 
Regarding Isolation, I would say they do isolate pretty well, I haven't really compared them with Bose/Beats but they use active isolation and these are passive. Still, I can assure you , traffic noise, metro announcements, irritating people nearby will be blocked off and the leakage is also under permissible levels. You will never be able to crank up the sound so much that they start leaking, they will just blow your ears before that , so don't expect much leakage at reasonable listening levels.

 
Sound Quality-
 
Lows/Bass- Now, They are bass heavy headphones, Not nearly as bass overpowering or extenuated as other headphones, but they definitely have a LOT of bass. The one thing which i noticed was that the bass did go fairly  low, but was not as tight for my liking. I really do advice you to go for a Fiio E6 if you intent to use them with ipod/pmp, Otherwise you can go for Fiio E7/10 for laptop. Post use of an amp, the bass is really tight and extended. Still , these headphones offer the best bass amongst Sony ZX700/Shure SRH840/ Beats, so for bass lovers they are perfect.
 
Mids- Hmmm..Don't compare with 500$+ category, The mids are still pretty balanced and neutral sounding. I still think that Sony ZX700/Shure SRH 840 has a bit forward range here, but overall when you listen to the M50 , the sound comes really balanced and pretty natural, You could always adjust the EQ for your need. Mids could be regarded as a lower point.
 
Highs- Again, pretty relaxed and a bit bright. It does have a brighter profile then some others. This could be both a downside and positive, I still think that M50 manage the highs quite well in its price range.
 
Vocals/SoundStage- Vocals are clear, though the bass can sometimes overpower if you chose the bass boost or turn the amp to high bass. Still I felt these headphones have a good vocal range. Soundstage surprisingly is pretty good for this type of headphone.
 
Genre- These sound good with most, Electronic, Hip-hop, Techno, Metal/rock,Dance/Party etc. Perhaps, accoustic and jazz/classic music could be better suited with Shure's as they have a better midrange , though you compromise on bass and the highs.
 
Additional Thoughts/Information- Do get an amp for them, need not spend 200-300, but anything under 100. I think for portable users Fiio E6 does the job well, if you use them primarly for home/laptop, consider getting the Fiio E7/10. The bass seems much more tighter and deeper and the overall sound is improved considerably making it rich .
 
Final Words: When a device gets so many positive reviews there's gotta be a reason, and the reason is the all in one package which ATH M50 gives you. Shure SRH840/SONY ZX700 are headphones you can look as well according to your needs, but to sum it up- You can't really go wrong with these, The overall sound quality is very good for the price and their ability to be used for portable purpose increases their funcionality. Comfort wise, stretching the headband really helps and would eliminate the clamping effect and you will get used to the earpad.
 
I give them a solid 4.5 star Rating.