A few things have struck me about the construction of the D5200. First off, I love the look of them, and all the metal parts seem well designed and executed. The headband seems a little too constricted, as in the curve isn't broad enough and I can see that causing some issues with people who are sensitive to hot spots on the top of their head. Not a problem for me, but I can see that as a possible issue.
But my main thought concerns the wooden cups. I've been a woodworker most of my life, so I know a little bit about exotic woods, and have used them from time to time in my projects, mostly as inlays, but occasionally as the primary wood. Denon chose zebrawood for the cups of these headphones. Zebrawood is a notoriously finicky wood, prone to twisting and cracking. It takes a lot of care in drying the wood to get good results, and even then, there are a lot of pieces that turn out unsuitable for most uses. So, they were starting with a self-inflicted penalty. Teak is far more stable, for example.
Then, once they have an exotic wood for their cups, they put a finish on them that is almost opaque? Why would you obscure the grain of the wood so much? These are some odd design decisions.
And as a final note on physical characteristics, the pads are not designed for people with large ears like myself. My ears don't quite fit inside the openings, and this limits how long I can wear them. Not painful, since the pads are so soft, but they become a little bothersome on long listening sessions.
Not ready for more detailed reactions to their sound. Still getting used to them, but I will say I'm enjoying them for the vast majority of my music.