I've met and spoken with more than a dozen Jetstar cadets and former cadets now flying the A320.
They all say pretty much the same thing.
1) OAA/CAE is disorganised and you need to be on the ball to push thru
2) The Jetstar cadetship is pretty much what is advertised
3) Probably 90% of cadets who start the course end up flying for Jetstar
4) They are happy with the deal and the way things turned out for them
It's tough to get a spot. I heard something like 1% who apply get an offer. The psychometric testing and interviews must be effective at choosing the best candidates, judging by the high completion rate.
The Jetstar cadets I met were a little bit more mature, rather than being 18yo school-leavers, and came from a wide variety of backgrounds. One really switched on Jetstar cadet was formerly a builder in his late 20s.