I was positively surprised about the aesthetics and overall build quality.
They look much better in real life than on the pictures on the web. Earpads and headband are very
soft and comfy, though they could be a bit larger, especially for my large ears. Getting a good seal and comfort though.
I think for portable use the bass emphasis is just right, though it would be a bit much for my personal preference in a quiet environment (although the bass is just very moderately emphasised and less than many in-Ears and full-sized headphones - e.g. the Meze has got less bass than the 1MORE Over-Ear Headphones).
Sound quality seems quite solid so far, especially in the midrange and treble department - good mids and treble details.
Some slight sort of weakness regarding sound is the bass - should be a bit better refined and more solid, with slightly less distortion in the sub-bass at this price point (but I'm burning them in anyway...). Bass is actually better, it was the source (Blackberry Q10 - don't judge me, I was too lazy to grab one of my dedicated DAPs) that produced the distortion for some strange reason - comparing back and forth between the DX80 and the simple source (Q10) I initially used, the simple source (Q10) produces some distortion in the lows with the 99 Classics - on the DX80 (and other sources except for the Q10), the lows are better and show less distortion and more control, however they could be a slight bit better resolving and quicker (treble and mids are higher resolving than the lows from what I perceive).
Overall initial impression is relatively solid and good nonetheless.
Suggestions for improvement: the cables - they're rather prone to microphonics because of the fabric/polyester coating. Imho above the y-split, the cable should be coat-less (similar to HD 800's cable).
Just a few very initial impressions from the first few hours of listening (so take them with a grain of salt). Might write a review sometime, but probably not before late spring/summer (which would be the earliest date; got different things on my schedule first).