It's better to have a shared home-folder for this, since all user settings are in the home folder. Just make a seperate home-partition when using the Ubuntu installer.
Copying all files to the other Linux-partition would take unnecessary much space on the hard drive, but I understand why you want it.
Shared /home it is not a good idea unless you use different Desktop environments. It can even crash desktop settings and the login time is much more longer.
Now you can copy your .firefox folder from Fedora and paste it into Ubuntu. You will have your benchmarks, themes and add-ons copied... However if you want to use 2 Distributions you would have to copy such folder every time you login to another.
Vahan Harutyunyan(Brainstorm moderator)
wrote on the 28 Aug 11 at 16:55