I'migrated from Netscape Communicator 4.79 to Mozilla 1.0RC2. I had to manually export my addressbooks to LDIF in Netscape and import them later in Mozilla. That 's no problem for me, but since you have a so wonderful migration that perfectly imported all my old settings and email, IMHO most technically not so experienced users would really appreciate adding an automatic addressbook import to the profile migration. If you decide not add it, think at least about a HOWTO, describing the process.
*** This bug has been marked as a duplicate of 35509 ***