The M50s sound excellent to me when listening to Tool or Rage Against the Machine, which both seem to favor heavy, driving guitar and bass lines. These headphones are a great buy, and they do not really have any major faults, as they sound good across many genres of music. A great, versatile pair of headphones. The overwhelming majority of people that have purchased these are very happy with them. The reviews, both from professionals and consumers, appear to rate the M50 very highly.
You will probably like them very much. If you can find a good deal for them, at a reputable establishment, I'm confident that you would be very pleased.
The cord is very long with the straight-cable version. (11 feet/ 3.3 meters) There is also a coiled-cable version available. Just something to keep in mind if you plan on using your headphones on the move.
Ideally, it would be preferrable to try out a few headphones, but I understand that this is not always a practical solution for eveyone. I listen to a wide variety of music, with a bit of everything in my library, and I would highly recommend the M50.
Good luck on your headphone search, and I hope that you enjoy whatever you finally decide upon.