When I heard the Burwells, they were being played at low volume and sounded not at all piercing. But, it might well be the case that they would behave poorly at higher volume levels. That actually is an issue with horn systems, particularly when they are not really large in size. As volume goes up, horns tend to become "shouty." I did not get a second crack at hearing them so I may have missed the bad behavior.
I heard the GIANT Von Schweikert speaker/VAC room a couple of times. One audition was horrible sounding--very bright and brittle sounding, but, on another occasion, it was pretty decent (though hardly my choice for a system well north of half a million dollars). The better sounding demonstration was at a much lower volume than the one I could not stand, so it might simply be a matter of inappropriate volume. I get the feeling that the people running demonstrations think that volume levels have to be extremely high to impress the public; I am more impressed with systems that deliver great sound at low volume.
As for the Classic Audio/Atmasphere room, it was bright sounding and also brittle sounding for my taste. In other years, it has sounded better, but, the brightness has always been a part of the sound.
Another room that I liked that I forgot to mention was the Conrad Johnson room with the "cheaper" model of Tidal speakers.