I'll try to keep this short. We used these headphones along with the monitor (M40fs) version, and Sony 7506's for production/broadcasting.
Pros: Sound/price ratio (unbeatable), comfort (really snug, so it won't go anywhere even when headbanging, soft insides), sound sealing (you can't hear anything softer than normal conversation if you tried), durable wire and plug, one eared listening a piece of cake.
Cons: Parts for the headphones don't seem to be easily available, can get warm inside, 1/4" input means an adapter is necessary for most MP3 players, no apparatus to wind up the REALLY long cord, no folding for those who care about that.
Comparing to the M40fs, the sound is sweeter with great trebles and bass, and it feels like a cushion inside, while the M40 is really flat and has a ring inside instead of the large cushion so it feels more open. Based on the prices, it's easy to pick this over the M40, unless you plan on doing audio engineering.
Comparing to the 7506, there is less treble and more bass, and they feel a bit more bulky, with rounded plastic versus metallic feeling flat sides. The one-ear listening is done differently, with the 7506 flipping and the A-T's twisting, and the cord for the 7506 is coiled (though more delicate). The value comparison is incomparable.