Pros: Good sound isolation, loud, swivel cups, fairly durable
Cons: ear pads (quality and also mounting)
First a note that all ratings are in the context of using that as a DJ headphone. Going by audiophile standards it would be lower.
The reason I've emphasized use as a DJ headphone is because that's even what they were originally marketed as. Can read all this on wikipedia but to summarize Sony has four headphones in this series: (from oldest to newest) MDR-V6, MDR-V600, MDR-7506, and MDR-7509HD. The V600 was created in response to a lot of DJs using the V6. It emphasizes bass and can be loud in the treble range as well. This is intentional because when queueing DJ's will usually either match based on the bass or high hats.
The MDR-V600 are also fairly durable for being all plastic. The platic is fairly solid and if they drop on the floor I'm not worrying if they're broke. Also from an audio standpoint they can take a beating. They can handle up to 1W of power (this is a lot for this price range) and are 45ohm, so they can get pretty loud.
My main gripe about these are the ear pads. First off they're oval shaped and meant to conform to your ear. This is also what makes the bass so powerful and also isolates the outside noise well. First problem is they're the Sony leatherette pads which Sony uses on a lot of their headphones. It's well know that it tends to break down after even a little bit of use. Second issue is the way they are attached to the headphones. They slide into a channel that allows them to rotate fairly easily. Problem with this is the pads aren't designed to rotate, they are meant to be in a single position. This can accelerate the pads going bad if other DJ's borrow the headphones and swivel them around. This puts stress on the seams of the pads and will cause them to break open. This is what happened to mine after 5 or so years of occasional use.
The good news with the pads is you can still find replacement pads if you search hard enough, but there aren't any upgrades you can do like you can with the MDR-V6 or MDR-7506.
For the price I'd highly recommend these for DJ use. If you just want to enjoy music and want a fairly balanced pair of headphones, keep looking.