Well, I took the PSM II exam a few days ago, leaving time to give some thoughts about it. So here is a quick review of my experience, hoping it will provide some useful tips without spoiling for the future candidates.
The exam had 35 questions, about 2/3 of them were essays. Answering to them all in two hours is pretty challenging in my opinion, for a non-native English speaker. I personally left some blanks, so be ready to catch the global sense of some potential multiple sub-questions pretty quickly, and consider not having time to review them. Get straight to the point while typing your answers, the timebox is short, no doubt about that.
The content was anyway pretty amazing, the challenge intense, like a philosophy exam during my school days. :) You can't get an answer just out of the book, your brain and SM's reflexes are your only tools here. The topics are various for that amount of questions and can be a bit "out of the road".
I couldn't agree more with Dominik regarding his advice to pass the exam, especially about experience: yes, be a Scrum Master for a while to acquire the expertise and reflexes. Having played the role of Product Owner is also a great plus. Had the following link with the token order, that I couldn't find elsewhere (http://www.scrum.org/Assessments/Wa...ut-Scrum).
Those advised requirements are not enough, for a PSM II exam at least, in my humble opinion. Oh, and also pass the new open PSD I assessment with a great score before!
Hope this answers some questions around the Scrum community. I don't have the results yet, but in any case, taking the exam really worth it!