I just received my M50s earlier today, and have been thoroughly impressed by them so far, especially for their relatively low price. I bought these because I needed a pair of closed cans for home recording.
I've never heard headphones (or anything, for that matter) reproduce frequencies as low as these cans. Even my DT990\250 Pros don't go this deep; at least that's my impression right now.. I'll have to do more critical listening later. The highs are detailed enough, but not shrill and sibilant. Overall, I'd say the are the most balanced cans I own. I think the bass is just about perfect, not too much not too little, and goes plenty deep. The mids are a little recessed, I think... but I'm not even sure about that
- might just be me not being used to listening to closed headphones.
These aren't as detailed as my other headphones, but these are also less than half the price as the rest of my collection. As far as closed headphones goes, these are the most comfortable ones I've worn so far. I don't get why people say the clamping force is too much. Maybe I just have a small head or something.
The ATH-M50s get two thumbs up from me.