I too was at the meet today and while I could probably never write something as detailed as the other two guys, I will say this: out of all of the other headphones at the meet, I went back to listen to the 400i multiple times and I borrowed them from the HiFiMan crew to listen to on other setups. I definitely plan to buy these headphones the moment they become available.
I asked them about when they would be out and their response was that it would be sometime in August, probably about a week after the 560s. On the other hand, the info sheet that was on the table said sometime this month.
These were probably my favorite headphones at the meet and I would recommend listening to them if you ever get the chance