Tuts,
I really wouldn't worry about it too much - have a look at the fail rate and make up your own mind!
It is (well was, I did the 'old' style IOT), however, a right royal pain in the posterior. I thought it was much more of a 'how much do you really want to be in the RAF' test than an Officer Training course.
I wish you all the best - bring a waterproof sense of humour.
MT