Huh...
I just did this to my M50's pads, and instead of bringing the mid forward, it was more like it cleaned up the upper high frequencies. Whereas it was a mess in busy songs before, now upper frequencies have a nice ring, and seem to extend even further into the abyss. In the process, bass got tighter and quicker, sub bass is less pronounced, and it overall sounds a lot cleaner!
But midrange seems to have suffered the most. Whereas it sounded warm and full before, it now sounds very clean and lean. I don't dislike it, since I don't listen to vocals much, but it definitely make some songs sound a lot colder and more anemic.
I'll have to hear more to see if I'll like this change. So far, it's positive for classical and busy rock songs, but it's killing quite a few vocals.