I suspect by now if you're intested in Apple's new operating system, MacOS Sierra, aka OS-X 10.12, then you've already read a lot about it, and likely downloaded and installed it. Good luck there, and I'll just add my comments from yesterday's day-long affair with it.
First, the whole download, install, reboot, review, change, update apps, reboot again, like 4 times, for changes or recovering memory took just over 6 hours, with the rest of the day working on the problems, some of which weren't resolved until this morning.
Anyway, some thought on MacOS Sierra.
First, the console window looks and works differently, and it sucks. I like the old one, but more so this one for another reason, the endless stupid chatter that didn't clog the console in OS-X 10.11. It's mostly geek shit literate users don't need to understand problems with applications the console window was useful to have.
It's clear programmers forgot to code out comments in the applications before releasing them because they're all just repetititive technical chatter about what the computer is doing than anything useful to help see what the app is doing or not doing.
A good example is that the Time Machine (or what HD you use) doesn't have the same basic information it wrote to the console window under OS-X 10.11 about starting, working, memory, HD's, files, etc. Now it's geek talk you have to be a programmer to know but nothing useful about the actual backup.
On the backup, the widget for it no longer works because it's written for the El Capitan version, and the management of the widgets (plus/minus signs in circles) doesn't work anymore, or continues to not work as it didn't work under OS-X 10.11.
This is because they completely rewrote the backup application, something they didn't really need to do after they fixed and refined it over the life of OS-X 10.11. It's back to square one again. Apple keeps reinventing the wheel and breaking it, instead of just refining it.
Onward. This has to be the slowest version of OS-X in its history. Even when working normally, the spinning rainbow wheel is a common response from the computer. That and it keeps having problems with bluetooth to the mouse, taking 2-3 clicks before it responds to switching apps.
Another thing I noticed is the softwareupdated daemon. It's used by the Apple App and iTunes stores when you install or update apps (iTunes moved to this daemon from it's own daemon). The daemon eats memory, using ~1.5 GB's for almost any update, smaller updates are 500 MB's to 1 GB.
The problem is the memory isn't released and can't be recovered, even by the daily maintenance, which moves it to inactive memory, the price Apple says makes reusing apps faster. I'm ok with that but not at 1.% GB's worth for one daemon. It's more than the kernal task uses.
If you don't want to keep it there, you can only update apps weekly or so and them reboot to recover the memory. Hopefully Apple will fix this, but then I'm not holding my breath with Apple updates anymore.
In additon, like many before me have noted, I can't get the debug menu option in the Apple App store (I have the preference set to show it) to clear the cookies, which can be done manually by deleting the files before opening the app, and reset the application.
And typical with Apple with the war with Adobe, it's installs more controls with Safari over Flash in browsers, one asking the user if they want to use flash on a Web page, but you can click, "Always use" to get on with the browser.
And Apple kept the great, simple bookmarks editor with just a cosmetic change (from STP) which is ok. It's easier to read, but a little harder to move bookmarks without scrolling. This editor is the best of all of the browser bookmark editor, especially Google's Chrome and Chromium.
I have tested all the apps yet, some were removed when the installation flagged them for incompatibility with Sierra. I use App Delete which is a cool little app for removing all traces of most apps, but you have to ensure you don't remove files common with later versions you may have.
I like to keep 2-3 versions of apps, more with Adobe since they last longer with upgrades, and because I prefer them over newer versions, eg. Cookies and Mail Satellite. Some older versions still may not open or work, but the installation didn't flag them as obvious.
I did find Bartender 2.1.6, supposedly Sierra compatible, doesn't completely work with Sierra, so they have some work to do, and hopefully soon as it's the best I've seen for managing menu bar icons (apps).
Anyway, that's the personal notes to date, and I'll add more as I find them.