My new HD650, and they are clamping my oversized noggin like a vice! When I switch back to my K701 it's like slipping on an old pair of tennis shoes. The only comfort issue I ever had with the K701 was the middle pad on the headband, but it either broke in or I developed a protective scalp callus long ago. The oversized earpads are like pillows on those things, and allow room for even the largest ears. I can't believe more people haven't complained about the size of the earcups on these things (HD650), as I have barely enough room with average-sized ears. Hopefully these vice grips don't take to long to ease up the tension.
Other than that, I'm really enjoying the sound of the 650. It's a little more veiled than I had imagined, and I can't believe anyone would ever want more bass. At least I have something to make recordings I couldn't listen to with the K701 more accessible, and rock ROCK harder. I doubt these will ever be my preferred headphones of the 2, but it's too early to judge. Now if my WA6 SE would arrive sometime soon...