My ceiling is flat and about 99 inches high, and the room is rectangular.
Those are key attributes for successfully using Dolby elevation speakers.
I have two systems, the big 5.4.4 HT with 4 JBL SCS8 Atmos overheads (same as used in Dolby Cinemas) and a 5.4.2 media room setup in a spare bedroom with Elac UniFi L/C/R and Elevation speakers.
I also have a Smyth Realizer A16 headphone processor loaded with a mapping of my big HT rig in the media room so I can listen to Atmos over headphones.
The media room is acoustically treated to a minimal (by my standards) level, with blackout curtains covering floor to ceiling the rear 3/4 of the room, and the entire back wall is covered with a thick carpet hung 3" from the wall (that's a super-effective cheap 'treatment' that also happens to look nice if you get a pretty carpet). So minimal reflections from the back or sidewalls.
OK, so how do they compare?
The media room system, although costing 1/10th of the big system, sounds very good. The Atmos bubble is there, and movies sound great. Since this room also has an LG 65C9 OLED, We actually use this more hours per week than the big HT. And the sound never disappoints.
So elevation speakers work very well if there is minimal to no reflection off the back wall, and likewise, no reflections from the sidewalls to smear the localization within the immersive bubble.
I find the~$250/pair Elac elevation speakers a great value, and being coaxes, their imaging is good.
Now, the big HT is amazing, and as I noted, not using as often, so whenever I do go there on weekends, rediscovering just how superb the sound of huge ESLs in a treated room is a joy. Atmos music is a real treat, and those SCS8's (fed 200wpc each) can sure keep up with the MLs.
Funnily enough, the atmos bubble is slightly less sharp than the media room, and that is because 6' tall line-sources are not as 'focused' as a monopole with a single tweeter. Also, there is less vertical distance between the top of the ESL and the center of SCS8 (about 3+ feet), so all that makes it less razor sharp. But for music, it's still the best sound I have.
So absolutely nothing wrong with using elevation speakers. Just like any other speaker, room setup will have a lot to do with the quality of the results.