Just listened to a pair the other day at Best Buy. First off, the build quality of the Mixrs is well above and beyond that of the Solos and the Studios. You do not get any sense of cheap plastic like you do with the other two. I flexed the headband a bit and they felt very sturdy in my hands. The strange thing is, although I love the way they look in pictures, in person they're a bit disappointing. No doubt they are still very attractive headphones, but actually holding them and flipping the earpieces back and forth kinda' made them lose their magic. What ruined it more for me was when I put them on. Granted this is a floor model and I would have to own one for a while for it to properly conform to my head, but man was it uncomfortable.
The clamping force put a lot of pressure on both sides of my head and the circumaural earcups felt stiff on my ears. I guess for DJing one would need a strong grip, but geez. I have a medium sized head(if my Old Navy hats sizes are correct) and I had some initial discomfort with my V-Moda V-80s(which took about 2 weeks to get comfortable) but it was nowhere near the vise-grip I felt with the Mixrs.
As for sound, and this is coming from a guy little experience analyzing headphones, they sound like they are part of the Beats family. I found them to be somewhere in between the Studios and the Pros, slightly less bass than the Studios and slightly more muddy in the midrange than the Pros. Granted, my song choices were limited since I was listening to them at a Beats kiosk where you have a choice of 4 song genres most of which I'm not very familiar with, although I do like the Black Eyed Peas. Until I can listen to stuff I normally listen to, I can't give a definitive answer to whether or not they sound "better" than other Beats. All the Beats I've ever listened to were at this same kiosk pumping out the same 4-5 songs over and over. As far as I can tell they are the most attractive, most uncomfortable pair of Beats. But they're still Beats.
