I too bought the PM-3 two days ago, I had tested them before briefly, and now I tested them thoroughly for one hour, and another 2 hours compared with Meze 99 Classics, Meze 99 Neo, Momentum 2 AE, B&W P7, NAD HP50.
Meze Classics have WAY more bass in comparison, and more pronounced highs also, and are more efficient. I liked them too. 99 Neo even more bass, a bit loose and bloated, general sound not as well integrated as in Classics.
Considering sound and comfort the PM-3 was the winner for me, I like them very much.
I tested all of them with my HTC 10 / Poweramp 3 Alpha / flac. It drives them very good.
One thing I observed: the sound of my new PM-3 is a bit congested out of the box, bass seems a bit weaker and high mids a bit overemphatic compared to what I heard in the showroom unit that is available for testing since 2015, so it has a lot of hours.
Already after listening one day, the sound seems to be more like what I heard in the showroom.
What is your experience with burn-in regarding this headphones?