PaxBoy - there is problem with your link. Although displayed correctly the link includes PPRuNe before IAPA. (Actually hard to describe, but if you click on it you will see what I mean)
True, IAPA could assist with disputes but one should be cautious. Tbey are not a 'not-for-profit'. The cost of membership likely isn't worthwhile for an occasional traveler. If you have an issue with an airline the national DGCA/CAA/etc and/or consumer organisation could be a better route.