As mentioned previously, there is one more late-l10n checkin. The good news is that there are no more to go. The bug that Mark Banner (Standard8) just checked in is:
Bug 455812 (nsAutoSyncManager should expose a scriptable XPCOM interface to allow monitor background download operations)
This adds one string into mail/locales/en-US/chrome/messenger/messenger.properties called "autosyncProgress".
It will be visible on the status bar when our new auto synchronization code for IMAP is working and downloading folders in the background.