After returning from vacation, I am finally catching up. Thus, within the last week, Apple has released the latest update to the iDevices, iOS 12, and the newest version of the Mac operating system, 10.14 Mojave. I have updated all of my devices accordingly, and I can tell you that these updates are all quite smooth and should pose no issues for those who are usually timid or nervous about making immediate jumps. There are, to my knowledge, no serious accessibility issues to be found and the bugs are minimal at best.
For an overview on MacOS Mojave,
the good folks at Applevis, once again, do a great job of summarizing them.
You can find a similar summarization for iOS 12 here as well