More than a little disappointed
I bought these after reading some old but very, very detailed reviews about the best headphones for recording and mixing. The MDR-7509s were rated very high by all reviewers (Sound on Sound) for closed-back designs. When I went to find a pair, I learned Sony had this new model and fellow musicians here on Sweetwater as well as folks on other sites seemed to be giving it a thumbs up.
They are modestly comfortable and do a good job of isolating sound -- keeping the sound in, not so much keeping sound out, which is fine for recording and mixing. I spend so much time with headphones on, it's actually preferential that I can hear someone calling for me or my kids starting to fight in another room, etc. They also provide an eerie clarity in the mid-range that is hard to define. It's not that the mids and high mids are hyped, they just sound very distinct. That's mostly a good thing, though it's something you really have to get used to if you're mixing in headphones (not ideal under any circumstances, but my circumstances are far from ideal).
The problem with these headphones is the bass. The bass is VERY overhyped. It's not only so saturated that it messes up my ability to judge a mix, it's actually uncomfortable to listen to pretty much any kind of content, even spoken word. Everything sounds skull-poundingly boomy in these. I really expected a lot more for the price of these (I know true "high end" cans are over $1,000, but this is a pricey set of phones for me). Unfortunately, I've repossessed my old AKG K171 cans from my teen son. They are physically uncomfortable as heck, but they are way more neutral for mixing than these Sony's, and the bass is not overwhelming to the point of ruining everything.