Thanks to Polk Friends and Families, I bought this as my first pair of HP. I can't make comparisons to other HP's. However, I want to comment that it really made a HUGE difference in the last few days of burnning in. It's been a WOW experience to me.
I was actually quite disappointed when I listened to it right out of the box. I'd always thought that it'd be either a Sennheiser, Beyerdynamic, or AKG of that nature if I ever wanted a HP. So I wasn't sure if I had made a good purchase. I know how my music should sound through my Focal. And I thought this HP really sxxks. It sounded so congested. It's not like there was any sound missing, but they all sounded like coming from a long distance without clarity. There was also a obvious recess on the mid range so that the vocals were dimmed.
Then I turned on repeat on my player and just let it sit there for the day through a list of different music. Everyday after about 10 hours I then listen to it. I've been doing this for the last 3 days, so it has about 30 hours in so far. What I can say is that I can hear a difference after each day. Out of curiosity, wife checked as well. She didn't know that it needed a burn in but she said to me "wow, why it sounds so nice now!". The sound just opened up with more instrument separation and transparency. There is more dynamic and the bass became authoritatively deeper that can literally vibrate the pads.
Sound stage gets wider as well. If I drew a 2D square around my head, sound can come from each corner or between my ears a bit above my forehead. Then extend that sqaure further away to a 3D stage, I can hear now 8 corners of possibilities. That sqaure can be wider and away depends on the music. (I need to say it requires high resolution music and different music can sound a different stage based on how they were recorded. Mostly I only hear 2 to 3 corners in the same piece of music.)
Again, I can't compare it to other HP's but I want to say it's darn good. I'd suggest that don't even listen to it or make a judgement until you have at least 30 hours of burn-in. I feel a bit of mid-recess still when I have the volume very low. The mid sounds good when I turn up the volume just a bit more. A good thing is that the mid doesn't become overly bright when I turn up the volume to get more bass. I am hopeful that it will open up more with bigger sound stage when I reach 50 hours or more.