So far, I've run into two major annoyances with Windows 10 1803...
First is that the mobile hotspot function (sharing a cellular data connection to other devices via Wifi) has been gimped, and trying to activate it just results in an "To share your connection, you need to add this feature to your cellular data plan first.
" - message:
Information around this is very scarce at this time - just a handful of search engine hits. From a post on the italian Microsoft forums, it seems you now need a Store app published by your mobile phone provider to use this feature. WTF, really? I've been tinkering for quite some time to find out where Windows looks up if using the hotspot is allowed or not, to no avail. Also see over here on Mastodon
The other problem is that powersaving for the first gen switchable graphics in my old notebook doesn't seem to work anymore. In previous versions of W10, the integrated Intel graphics would be used on battery, using a lot less power than the AMD graphics chip.
As for minor niggles, it's not possible anymore to unconditionally set a network connection as "metered" to restrict Windows updates and background data - you'll have to set a daily or monthly data limit for the network, and then tell the system to always restrict background data (instead of within 10% of reaching the limit).
It really seems that W10 1709 was the sweet spot for this old notebook, but after I didn't see any immediate problems with the new version in the week directly after upgrading, I already deleted to rollback version...