[X4U] Mail.app vs open source mail?

[B. Kuestner]

One thing that kept me from migrating is lack of integration:  
Thunderbird does not support Spotlight nor OS X's Addressbook.

It's not in your list of priorities, I still found it worth mentioning.

As for migration, I think this site is obsolete, because as of Tiger  
Mail doesn't use mboxes anymore. Always consider migration via an  
IMAP server. But it can be a pain for large amounts of e-mail. You  
have to setup your local IMAP server on the machine for that. The  
advantage of it: You could use both applications for a while and just  
try them out simultaneously. If you go that route, please post what  
you did and how it worked.

Björn