Will Twitter at 280 chars suddenly become a bastion of rational, calm, thoughtful speech, celebrating what little good Humanity has in it? Or will people, better able to understand each other, get further enraged and end the world? Let's hope!
Currently I won't upgrade, I have a Fusion Drive which isn't supported by APFS yet. I'm not desperate to upgrade for that, HPFS+ has never hurt me yet, I keep a reasonable backup schedule, my source control is backed up.
I waited until last month to upgrade to Sierra, I was working just fine on Mavericks, and only upgraded because Xcode (UGH!) required it. So my advice is usually very conservative: Wait until you absolutely have to.
That said, there's new stuff that is interesting in High Sierra: VR and new image file formats. So I'll likely upgrade sooner, once I see fusion drives supported and hear no more horror stories.
On a side & musical note, I'm already super tired of the California theme. The other 49 states and hundreds of other countries don't like you that much, Cali.
"By June 1949 people had begun to realize that it was not so easy to get a program right as had at one time appeared. I well remember when this realization first came on me with full force. The EDSAC was on the top floor of the building and the tape-punching and editing equipment one floor below on a gallery that ran around the room in which the differential analyser was installed. I was trying to get working my first non-trivial program, which was one for the numerical integration of Airy's differential equation. It was on one of my journeys between the EDSAC room and the punching equipment that hesitating at the angles of stairs the realization came over me with full force that a good part of the remainder of my life was going to be spent in finding errors in my own programs."
-Maurice Wilkes, Memoirs