Alternatively, you could use a shared project to do sharing between
identities. It would not be 100% duplication, but then again, you also would
not have the same issues with simultaneous use.
In 2004, you can create a new project, and then share it out. Share it to,
say, /Users/Shared/Documents/Office Projects. In the original identity, you
can assign all your contacts and calendar items to the new project and they
will get shared. In the other user space, create a new identity with the
same e-mail accounts (this will work for IMAP/Exchange, but not POP3, unless
the option to leave mail on the server is kept), and then subscribe to the
project. (File/Subscribe to project... choose the Archive.rge file in the
project folder you put in /Users/Shared; make sure to switch it to share new
items added to the project by default).
You have to be careful to create new contacts/calendar items and attach them
to the project, but if you do, the other user(s) will see them.
Since IMAP/Exchange mail lives on the server, there's no problem having
separate accounts that keep cached copies in different local identities, so
you don't have to do any project maintenance w/ e-mail.
-nh