I'm all for the ability to process the ATMOS codec, and made damn sure to buy a receiver that could do so. A/B'ing ATMOS encoded material vs. the older stuff has been an eye-opening experience...even when down-mixed to 2.1
That being said....
I've had no motivation to go further than 5.1 With capable speakers sporting the right dispersion characteristics, proper placement (paying particular respect to the setup diagrams in most AVR owner manuals), and the right processor, 5.1 seems to strike the right balance, for me, of throwing sound all around the room without becoming an absurd chore to set up and maintain.