I've read about demos. Seems to be a mixed bag. Some people find upward firing speakers almost as good, others have indicated they don't like them. Speakerwise, I'm ready to go in one spare system (already have in-ceiling surrounds which I'll convert to Atmos and have speakers sitting around for the normal surrounds).
Still no word on DTS UHD in receivers. Denon and Marantz have announced upcoming availablity (in addition to Atmos) of Auro 3D for a fee. Also, current crop of receivers is half-assed for 4k video. For the moment, I'm at least waiting until I see a DTS UHD announcement (perhaps CES in January) and I'll make my decision after that. I have an attic above the living room in the main system (which is currently 9.2) and may before the end of the winter get in-ceiling put in for an eventual 11.2 Atmos system.
In my opinon, the important thing is the front soundstage with HT. I won't say that timbre matching makes zero difference for the other channels but to me it is less important.