After years of use, although I have to say that I didn't listen to them as much as they deserved.
They are the most neutral I have heard, they remind me quite a bit of the HD560s, just a click lower in brightness.
They are entirely made of plastic, with a very good cable that doesn't pick up any noise or have memory.
The bass for open-back headphones is at the level of the HD600, it doesn't go as low as some planar headphones like the Sundara or LCD2C... But it's definitely above the 400i.
They have an airy neutrality, they don't color the sound or feel in your head, so it might be off-putting for some when listening to music.
I would say they are flawless and very affordable, especially for professionals. For analytical listening, I would recommend the 1990pro.
In terms of comfort, the earpads are soft, but the ears touch the driver and the lobes rest on the earpads as if they were on-ear. This 3D wing system, when you put it on, feels like it's not even there, unfortunately, it's unstable and one side loosened more and I constantly adjust it on my head. Personally, I didn't like the 3D wing.
In the end, they are amazing headphones for professionals, not so much for everyday use when listening to music. They don't have the warm character of the 650s or the sparkle and bass of the 1990s, for example...