Despite their disappointing early problems, that are not uncommon with new sub/warship designs, in exercises with the US Navy our Collins class subs have 'sunk' 5 nuclear subs, 4 aircraft carriers, and several destroyers. Thus, they are clearly an effective deterrent.
An interesting 10 min clip shows HMAS Rankin taking part in the 2005 exercise Silent Fury with the USN off Hawaii. Despite the Americans cheating, HMAS Rankin avoids detection by the 5 USN ships hunting for her and "sinks" the brand new destroyer USS O'Kane.
