The lack of Atmos upfiring drivers aside, while some people will scratch their heads at a 3.1 soundbar + separate speakers for sides I actually think Sony did it the right way for good 5.1 audio.
After having used the Samsung HW-Q90R for a month I must say that I don't like the implementation of side channels in the soundbar.
Maybe I'm too used to my AVR setup in the living room (where side speakers are at 90 degrees from the seating position), but I feel side audio should be coming from the listener's left+right sides, not from the very far left+right front. Standalone speakers for the side channels are a must, in my opinion.
I missed the window for returning the Q90R due to circumstances out of my control, but I really wish I'd have gone with the ZF9 (or this new S20R) plus side speakers instead.
I'd prefer having proper 5.1 separation over getting Atmos capabilities, but maybe that's just me...
LE- What would be really nice is if at least one of the bunch would come up with a 5.1.4 solution: 3+2 drivers in the soundbar and two wireless speakers with 1+1 drivers (akin to what Samsung did with their rears for 7.1.4); or even go nuts for 7.1.4 with 4 wireless speakers (sides and rears)