Do I have to manually recreate all my menu preferences, default tab stops etc. or can I get 4.0 to recognize my old settings?
That should be fixed in version 4.0.1.
→ Bug 57061 - Not all personal data imported during install from /3 User Profile
Status: NEW RESOLVED FIXED
See also:
https://wiki.documentfoundation.org/ReleaseNotes/4.0#Most_Annoying_Bugs
How to read custom color from file (Libreoffice 4.0RC3)