There is one thing about login autofill I like very much about Opera: Username and pw are not filled in automatically. Instead, an orange border around those text fields is shown, indicating that you can press Ctrl-Return, and Opera will login.
That way, it just isn't so obvious that there is a login stored for that page - especially nice if other people regularly use the same account on that computer. Of course, this is really far from secure, but I like to know that others have to really know how to use Opera (they don't, normally) in order to use my forum accounts, e.g.. (At work at the windows box, that is.)
OTOH, this requires learning, and I understand that a browser should be as self-explaining as possible by default. So maybe this could be a config option?