I don't do Apple Atmos Dave ...so what is your take?
Like you, I've delighted in the three channel for years.
What could be better than drums L piano C bass R?
At least 50% improvement on stereo.
Comparing the Atmos sound field on the first track was a little dis-orienting from the opening notes.
On my budget 7.4.1, the "zing" of Mr Peterson reaching into the grand piano to strum the strings and let them ring, rather than located dead-center, seems panned hard left.
The bass answers hard right as on the SACD, the piano key-strikes remain left blended with the drums.
But as my ears and brain adjust during the first verse, the piano seems to widen out and wrap around the sound field in a pleasant way. The LFE thump of the bottom octave of the bass is perceptible, no kick in the mix. An enhancement IMHO, but depending on the size of one's mains vs three channel, YMMV.
The center channel is a mix of all three instruments at a reduced level, which seems to annoy some folks. But as part of the room mix it fills in middle of the front without calling attention to itself. The sides surrounds are quieter than the back surrounds, which have more signal and create a quad feel, but with things more filled in between the corners of the room than 4.0.
The fairy dusting from the ceiling speakers is more than ambiance in my perception.
No single instrument is soloed in a single speaker or pair, that would be gimmicky and ineffective.
Listening to this alternative mix compared to the floor level mix from 25% as many speaker boxes is perhaps enhancing my understanding of "object-oriented" mixes versus "discrete."
Comparatively, the grand piano seems a little cramped in the three-channel mix now.
Instead, even though panned left front in Atmos, its seems to swell to it's full twelve-foot length.
Ditto for the bass & drums, which seem to have a natural sound more focused than spongey from anywhere in the room, though not "discrete"as defined as a single instrument in a single speaker.
There's full range bass content in the back surrounds which benefits from large woofers.