I ran into a really annoying problem yesterday. In a small office of just three workstations (and two more that connect remotely), the computers cannot automatically connect to the fileserver on boot. Instead of using the username/password associated with the shared folders, it automatically connects using the AppleID, which works because the server uses the same AppleID. The server is a Mac mini running High Sierra also.
So let me explain. In the past, sometimes this would happen, where you would click on a shared Mac and it would sometimes try to auto-connect as the same user you are using on the current computer, or using the AppleID. But you click disconnect, then reconnect, and type in the correct username and password. Checking the box to remember the password. Once the volumes are mounted, you save them to the dock, you put them in the "Login Items" folder, and BAM auto-mounting network shares.
But now that does not happen. Now no matter what, it connects to the server using the AppleID. So the shares will be working perfectly. Then when you reboot, it auto-connects with the AppleID not the username. Under the AppleID, the shares are either not available or available but as read-only.
This is a pain in the ass for me, a tech person. But for "regular" people using the file server, this is a huge hassle. I'm pretty sure they don't even understand what the problem is when I explain it. They made a whole list of all the problems they are having with the new server, not realize that every single item on the list is exactly the same, "can't write to files on the server". It needs to be seamless and easy to use, something Apple excelled at once upon a time.
Addon: Also, one of the work stations is still on El Capitan and it does not have this problem. It seems to be a "feature" of High Sierra. (No Sierra Macs to test on)