I just went through an audition process for in ceiling speakers for my surrounds (B&W 805s for the mains, Velodyne DD12 sub, Bryston 9b SST amp, Onkyo 805 being used as a pre/pro) Listened to both the Thiel PowerPoints as well as the Triad Omni series.
For audition purposes, I focused on 2 channel performance (I was considering going all in ceiling).
When you were in the sweet spot, both had wonderful sound stages. Alas, the sweet spot was a very band of distance away from the speakers.
I thought the Thiels had slightly better imaging, but that could have been demo room dependant (different dealers, couldn't directly A/B the set ups). I thought the Triads had slightly tighter/more accurate mids and highs (Thiels were a little more sloppy to my ear).
I ended up going with the Triad InCeiling 6/Gold Omni's for my surrounds. Waiting on install, so can't speak to performance in my space.
Both units are a compromise in performance vs floor standing models. They are both extremely impressive for in ceiling speakers, and are relatively unobtrusive (the Triads much less so...they are flush with the ceiling surface rather than jutting down).
Both obviously lack meaningful bass performance and need sub support.
In the end, the price advantage and lower profile of the Triads won me over, as well as the tighter mids/highs (I'm a big fan of the B&W sound). Looking forward to getting them installed.