Rated 4 out of 5 stars

Extension works well. You can also use it to import your passwords to the 'login' keychain, even tough this is not the main intent.
But if you are looking into a way to use Firefox with iCloud keychain, this extension falls short. It integrates with the 'login' keychain, but iCloud keychain passwords are stored on the 'iCloud' keychain. That was a very close one, I hope the developer can make the bridge so the extension becomes 3 times better for iPhone users.

This review is for a previous version of the add-on (1.1.7.1-signed.1-signed). 

Unfortunately, Apple restricts the use of iCloud syncing to applications that are distributed via the App Store. Unless Mozilla moves to distributing this way (and requests permission to access iCloud when building the application—which seems unlikely unless they start using it), supporting iCloud does not seem possible. See http://code.google.com/p/mozilla-keychain/issues/detail?id=62