I haven't tried with outlook and what not...
-See pics calendarSub-folders.png, cantChooseWhereToCreateNewCal.png, & extraPartOfFolderName.png
-It kinda displays path wrong (shows full path) & you can't create sub-folders from the web-client yet.
-Sharing when sub-folder issue mentioned above.
-Checkbox state doesn't keep
Command line: zmmailbox -z -m
user@domain.com cf --view appointment /Calendar/subtest