This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
I found ExamLab very difficult. I think I scored between 58% and 76%.
The Master exams were somewhere between 75% and in the 80s.
I did not use the clock in any mock exam, i.e. sometimes it took me far longer than the given 3h for completing a test.
There were no insane difficult trick questions in the real exam although some needed quite a bit of attention to detail. There were no overly complex questions like some in the mock exams were sometimes it took me 20 min to figure it out.