I had a usual 5 speaker + two subs Dolby system for some years now. When my Onkyo 818 broke down, I replaced it with a Denon capable of Atmos. I spent another year with the Denon, that is just as good or even better than the older Onkyo it replaced, until I put 4 extra speakers on the ceiling. These are very similar to the front and center speaker, which makes them virtually disapper as single sound sources. My experience with mixed speaker models is not that good.
The Atmos effect is extremely dependent on the source material. It is like on a scale from inaudible to really impressive. There seem to be more movies that make use of the upper channels now, like birds in the sky, helicopters, planes etc. which can be quite surprising.
The first time my daughter listened to the new system, she instandly asked "do you even have speakers up there now?" The front height are up 10 foot or 3,3 meters, black on black and you hardly notice them with the usual living room light.
My two dogs love HD animal films that are not spoiled with stupid music, but have natural sounds. They are all "ears" and She-dog even barks at the screen when things get scary or wild. I think this is a a clear sign that Atmos works well

With most music Atmos works just fine, may it be streaming, CD or FM, even very old recordings. There are just a few recordings that seem to be extremely flat and reduced, just like a low rate MP3, when played with Atmos. I have not discovered what this funny problem is, these sound better in stereo or "all channel stereo" in my room. Maybe they have no useable information for the decoder.
I will not go back to anything less and want to add two more speakers in the future, but this has to be planed and carefully matched to the room. If you have the space and relative high walls, real Atmos is definately worth it. Don't go for any reflecting speaker extensions or the like, these are a waste of money, just like any "made for Atmos" thingys. Keep the quality and signature of your front speakers, otherwise you will not get a homogeneous sound experience.