Macrojack, I really, really liked the Oswalds Mill horn loudspeakers at RMAF. In fact, it was easily one of my favorite rooms. My only problems with the design were the extreme looks/low WAF and what must be an absolutely stratospheric pricetag, though Jonathan assured me I could afford it.
As far as sonics go, the Oswalds Mill horns were the most natural sounding loudspeaker of this type I have ever been around. They combined the immediacy/suddenness along with large variance between quiet and loud that a horn should provide, with the lack of irritating or unnaturalness. I felt it truly to be a coup of not small measure. Given their extreme looks and the poor quality of the rooms at RMAF, that surprises me. I have no idea how much they cost, but if I had the money, I would most definitely make the drive up to give them another listen.
The Avant Gardes seemed to have an "amplified" nature about them, where even acoustic music took on the feel of being played through electronics, along with that feel you get when you listen to a Victrola. It wasn't necessarily a bad sound, and oftentimes, it worked. Just that when you are listening to some music, because of it, it leant kind of an unnatural quality to the sound.
Personally, I thought the Acapella room was the worst sound at the show by leaps and bounds. Other than their ability to completely dominate a room and make a visual statement or play at jet engine volumes, I have no idea what anyone could see in such a product.
I don't have any experience with the Oris or Haigner, so anything I would say in relation to them would be a lie.