I recently picked up a pair of Q4s and 2 pairs of Q8s to act as surround and height channels in my theater room. I had originally been looking for Revel on wall speakers to match my Revel front LCR setup, but there wasn't anything really available except the Concerta2 S16 which is discontinued. In any case, the Q4/Q8 setup has been working great alongside my Revels, and I don't have any noticeable issues with timbre matching, although I did use Audyssey MultEQ-X to help dial things in.
The Q4s actually replaced an old pair of KEF T301s I had used as surrounds, and it's a huge improvement in overall sound quality and bass extension. Even though they are low profile on the wall, they can still dig fairly deep on their own. I'm able to comfortably set the sub crossover to 80 Hz, and nothing sounds stressed at high volume. These seem to be a really good option for general on-wall duty, and I'd be curious to one day set them up in stereo just to see what they can do in a 2.1 system. These could be a great alternative to a sound bar for a wall mounted TV, for example. I wouldn't be surprised if KEF introduced something in a similar form factor but in the R range.
The Q8s are sidewall mounted up high near the ceiling as front and rear Atmos channels, and the built in downward angles made it easy to mount and adjust. I really didn't want to ceiling mount and deal with separate speaker mounts, so these fit the bill. While they don't have the bigger, ported enclosure of the Q4, the Q8s still had decent bass extension probably from positioning near the ceiling/wall edge. For Atmos tracks, they had no problem delivering crisp height sound effects without sibilance.
For the money, I think both the Q4s and Q8s are great values as high quality surround/height channels. I'm not sure I'd be able to tell the difference between these and more expensive options for movies/television. Maybe for multi-channel music there would be more benefit to having full-range, higher priced alternatives, but I typically stick to stereo music.