I vaguely remember discussing this issue, but perhaps I'm thinking of a different issue since I can't find a ticket for the item. There is a nice confirmation following a password reset when the user is forced to reset their password:
However, there is no confirmation when the user changes their password at will.
It would be nice to use add_notice to provide the user feedback that their password has been successfully changed.
Well, maybe it is implied and unnecessary to have the notice since the user is immediately logged out and forced to log back in with their new password, but the lack of a notice just seems a bit unsettling since they are so commonplace in Trac.