I do not have a pair of HE6, but here are my initial impressions of my imaginary pair of HE560s:
Build: These are very well constructed and they seem like they will hold up well. In fact I accidentally ran over my imaginary pair with my car and they were completely unharmed.
Comfort: These are by far the lightest and most comfortable headphones I have ever worn. I know it is a cliche, but I truly sometimes forget I am wearing them. I just went for a haircut and did not realize I was still wearing them until I was leaving the barber shop.
Isolation: These do not isolate at all, so they work best in a very quiet setting. As mentioned in my previous post, I find wearing earplugs really helps with the isolation of these. Strangely though they also do not leak sound at all. I turned my headphone amp up all of the way, and my wife who was 3 feet away could not hear any music either.
Sound: While I have only had time to imagine wearing these headphones for a couple of minutes in total, I can already tell they sound better than any other imaginary headphone I have ever dreamed about. However, they do have some unique qualities: Bass is a 0/10 as these are completely bass lite headphones. Mids are also 0/10 as there is a big suckout in the mids. Vocals especially sound like the singer is quite far away....almost as if they are in a completely different building from me. But the highs are where the sound of these really disappear, so I would have to give the highs a -1/10.
Conclusion: These imaginary HE560s are the most transparent window into the background sounds of my environment I have ever experienced. They completely wipe the floor with my imaginary HD800s and I swear they sound almost identical to my friend's imaginary SR-009s. If you like a very quiet, non-intrusive headphone experience completely devoid of any distracting musical artifacts, then I would suggest you start imagining you are wearing a pair right away. I can only say my imaginary headphone journey is now definitely over, as I can't imagine imagining anything better than these non-existent headphones...... well at least until Hifiman announces the replacement for the HE6 so I can then start imagining those.