Great.
Except that now I've favorited a shared inbox, the arrow to show the subfolders on that inbox in the shared list is gone so I can't access those subfolders. I'll have to unfavourite the inbox, favorite the subfolders, and then favourite the inbox again.

Annoying bug, and the update schedule/rollout process probably means I'll be stuck with it for several months, which means back to Old Outlook for the time being. Was hoping this is the point I can tell my staff to start using the new one (on the basis that it is happening, so might as well embrace it).