If you go to the Google AdWords Certification Program Learning Center you will now see that Google is offering 4 exams, not one exam - to take and to earn your certification with Google AdWords. The exams include:
- Google Advertising Fundamentals Exam
- Search Advertising Advanced Exam
- Display Advertising Advanced Exam
- Reporting & Analysis Advanced Exam
There is actually a whole grid of courses you can review before taking the exams. I am not sure if you can actually take all four exams yet, but it seems like you will be able to do so soon.
We actually expected the tests to get harder over time, plus Google told us to expect this as well.
Forum discussion at WebmasterWorld.