I just had a very quick look through the reviews on amazon.com. At a first glance I can see only 2 bad reviews, 1 whos parrot didn't accept the harness, the other who claimed his conure had escaped because the straps snapped, believe me if the straps were in any way defective and about to snap then you would be able to tell, it would be like trying to tear a nylon dog lead in half otherwise (impossible). My only thought on this really is the owner allowed his parrot to keep chewing on it or was careless enough not to check the harness prior to going out.
If you want to look at the training process then Michael has an article on training Kili to wear one, step by step. It is alot better than the DVD that comes with the harness -although I did hear a rumour they have improved the DVD now. By the way, aviator is the make Michael has so you will be able to get an idea of exactly how it fits and the quality of the material.
Ps I don't work for the parrot universty, honest

they just really are the best harnesses I have come across.