First - and it's important to get this out of the way - I think "macOS" is silly. Yes, I know that we had iOS, which was fine because that carried the linguistic DNA of the iPhone/iPad/iPod. I thought that "tvOS" was a goofy but no matter - I mean, when do you ever really see that in print or media? I'll let that pass, along with "watchOS".
"macOS" just raises my hackles for some reason. We had MacOS back in the day (grumble-grumble-get-off-my-lawn) and that seemed sensible enough. That became MacOS X, which again seemed like a logical progression. Dropping the capitalized "M" just feels like a change made purely for the sake of change in order to bring the four operating systems that Apple currently puts out into some kind of thematic order. It breaks the history of their flagship product, and it's just dumb and bad and I'm probably old and grumpy.
On a happier note, with macOS (ugh) Sierra Apple have done a pretty good job of un-breaking something that they really screwed up on last time; removing RAID support. It's not an important feature for a lot of home users, but with Server setups on smaller systems that don't have the luxury of a dedicated RAID card and that need mirrored or striped internal storage it was a bit of a blow to see that removed in El Capitan. Imagine, if you will, my child-like joy when I cracked open Disk Utility in the latest beta and saw this:
My relief was palpable. No more fussing around with the Terminal, trying to remember the diskutil corestorage commands and generally pulling out my hair and gnashing my teeth in rage.
Now, if they could just fix the stupid name...