I have recently passed the 83-640 exam. I can tell you it’s a bit different from the usual exams. Microsoft has mixed this exam with the usual questions and 2 labs. Each lab contains between 7 and 15 tasks you need to do before you can continue to the nex lab or questions. Very strange but passing the exam is possible. Just have a bit of patience with the connection to the virtual lab. This is a slow link and you need to be slow with your typing in the commands (if neccesary).
I passed the exam after about 90 minutes. I passed with a score of 900 out of a 1000 points.