Well Mojave has been a pretty seamless upgrade for me at least. The quality push at Apple seems to be working. The only glitch I've seen so far is that on one of my machines, Finder is not refreshing properly so you see old files even after you move them.
The fix seems pretty simple, just delete the Finder plist at ~/Library/Preferences/com.apple.finder.plist and reboot and that seems to fix it.