Hi Showaard,
I went through FSP a few weeks ago and am awaiting an offer and yes the rumours about increased stadards are true and the RAAF is only looking at about the top third applicants in the distribution pool.
From memory YOU Assessment was easy, simple IQ test style questions, nothing to worry about.
Specialist skills assessment was a bit harder and and I think the only prep I did was mental arithmetic.
Assessment day wasn't too bad but lots of prep made it much easier. Know as much as you can about your chosen service and training pipeline and current ADF leaders as well as things such as the defence white paper etc. Also make sure you know what your motivations to join are and display some level of understanding about how your life will differ in the defence force (I encountered these subjects in my Assessment but they do differ.)
PM m if you have any more questions. Best of luck!