Had another thought. Right now, the confirmation message "Thank you %s, your account has been verified..." appears at the end of the login form. I realize this is because you are using the login_form hook, which appends stuff at the end of the login form.
However, in my beta testing, my users were confused by the message appearing at the end of the form rather than at the beginning. (You know how easily the average user is confused.)
If there's any possible way of putting the messages at the beginning of the login form or sending them to another form entirely, that would be optimal. Perhaps Register Plug could generate an entirely new form for just this purpose.
Just a thought.