I remember diagrams of some crazy 26.1 systems (or was it 26.4?) a few years back. It really went around the listening space. I too thought that it was cool to have speakers overhead, and I know that the more speakers that can be controlled (key there is the control of them), the smother a panning sound, or more precise a location can be emulated. However, until I get my own IMax dome, I don't know if I really care about more than 7.x Like Ben said, they can't get much out there in 7.1, plus people are now doing front wides/highs that aren't specifically programmed for. We basically have 11.x or 12.x right now and nothing is utilizing it.
As for what speaker to us, I think that a QS8 would work great. In the little sample video they talk about "simulating" an array of speakers overhead, not actually having a full array. Nothing fills an array worth of sound in a single box (or a couple boxes) like the QS8.
Of course, most people will be limited in ceiling height, so some sort of "in ceiling" model would need to be made, but I would wager that there would be some acoustical compromises in that type of design being "in-wall/in-ceiling"...
