I have exact same problem with windows opera 18.
I have no idea how to turn on traditional opera button that let to login automatically.
I don't understand why it was removed. There are no info about it at all on Internet, like people don't use opera...
I have to login to multiple pages every hour, and typing password every-time is pain in ...
I found some settings, and was surprised that I can see all saved passwords on all websites I've logged-in.
That does not make sense, if developers removed auto login button for security reasons.