In terms of concepts being tested, Marcus' exams are pretty good. However
you should understand the exam
pattern has been changed recently, since October. The questions in the new exam are relatively lengthy, almost always based on some sample code unlike the many mock exams that exists out there that are partly code based. Atleast that's what people say after passing the new test.
I would recommend you to do
all the mock exams without being biased whether it resembles the real exam or not. In addition to doing those tests, write a LOT of code.
Ajith