Migrate from Gmail to Google Apps and keep labels, read-status, stars and email date

Install imapsync:

Under Ubuntu:

sudo apt-get install imapsync

then:

imapsync --host1 imap.gmail.com --user1 username@gmail.com --port1 993 --ssl1 --password1 GmailPasswordHere --host2 imap.gmail.com --user2 username@YourGoogleAppsDomain.com --port2 993 --ssl2 --password2 GoogleAppsPasswordHere --authmech1 LOGIN --authmech2 LOGIN --syncinternaldates --split1 100 --split2 100 --allowsizemismatch

Done!