I agree with WBV, Stage 4 is an assessment of your ability to analyse your own performance as well as an opportunity to demonstrate flying aptitude. My experience was virtually identical to WBV's with similar tasks and questions in the 737 sim.
I was having so much fun, I forgot I was being assessed. When I was congratulated on passing the final stage it came as a bit of a shock because I'd forgotten that's what I was there for! The chop rate is low (compared to other stages), they have a good idea that you've got the right stuff by this point. Don't let yourself down and relax too much, but don't worry about it either. Enjoy the 73's left hand seat, it'll be a while 'til you get another chance to sit in it!