Biggest issue seems to be Nautilus. On 16.04 there seems to be a running instance always in the background so right-clicking on the “Files” icon in the launcher gives you a choice of multiple folders you can launch directly. In 18.04, right-clicking on “Files” pretty much only allows you to launch it initially into your home directory. Once it has been launched, however, the icon in the launcher behaves the way it used to. Also, in 16.04, Ctrl+H only shows you the hidden files in the active nautilus window. In 18.04, it displays the hidden files in ALL of the open windows.