I'm self teaching it at the moment and it's definitely the hardest for me out of all of the pure modules, especially some of the questions that come up for conics can be especially horrific or random (JUNE 2014 Q6) or super easy (JUNE 2013 Q1). Other chapters such as hyperbolic trig and differentiation or really quite easy and there's not much that they can throw at you in the exam that would throw you off for these topics unless you really just don't understand them.