Awfully buggy.
Just installed on Android. After syncing to my account it shows "no entries found", even though I have hundreds of saved logins in my Mozilla account.
Tried disconnecting my account in order to re-add it again, and can't find a way to do the latter. It just keeps showing the "Disconnect Firefox Lockbox" button, even though it (presumably) is already disconnected.
Will check back in a couple of months to see if it's more fully-baked. But right now this feels pretty pre-alpha.