Hi Farid,
As I mentioned below I found the simulator easier than the exam, but the simulator does give you a very good idea of what to expect in the exam.
I found that the exam simulators were incredibly useful, especially if you simulate test conditions (max 4 hours, no interruptions, no books to help, and using a brain dump sheet at the beginning). They do give an idea of what to expect in the test. However, the actual exam was harder than the test, so be careful if you want to do two passes.
The way I approached it was if I could not answer a question in 2 minutes I guessed an answer and marked it for review.
The reason I guessed was if I ran out of time I still had a chance of getting it right.
The calculation questions are not the hardest, as long as you know the formula and can use the computer's calculator you will get them. It is the touchy feely questions that you have to answer what would be the best thing to do, or what would be the next thing to do.
Personally, the simulator quizzes were handy to get a feel for the types of questions and format of questions. They help prepare me in that respect before I started studying so I would understand what I'd be quizzed on. Once I began studying, I took the quizzes before and after relevant topics for the same reason.
The actual full length exams, while comprising the same questions, were a different beast. Given the larger set of questions and a commitment to aiming for completion within a time frame, the exams would give a much better idea of where I was at in my preparation for the Exam.
Training for Project Management Professional (PMP)®, PMI Agile Certified Practitioner (PMI-ACP)®, and Certified Associate in Project Management (CAPM)®