Here are my observations and some tips you may find useful:
In the beginning of the exam, you are required to answer several questions about your Java experience, which is not included in your test time. However, when you start the exam, you need to answer a few more questions and accept the terms and conditions - this time IS PART OF YOUR EXAM TIME! It can be confusing, but now at least you know it.
I used Phil Heller's book to prepare. When I bought it, it was the only book covering the new 1.5 stuff. Warning: reading this book is not enough. There are a lot of questions on the exam about stuff, which this book does not cover! I guess the authors wanted to be the first ones to publish a 1.5 preparation book - it still focuses on 1.4 topics, the new topics are only briefly covered, sometimes contradicting other text in the book. (E.g. at one place the book mentions the new covariant returns, but at several other places it says that the return type of the overridden method should always match the type of the super method, which is not true in 1.5). Moreover, the book is supposed to prepare you for the SCJP 5 exam but there are sections about bit shifting and the Math class, which are not part of the new exam.
Another thing about the exam: It has been mentioned before here, but now I know it for sure - if you try to review/correct a drag-and-drop question, your previous answer is gone. Be careful with this. I dont understand why Prometric dont fix this in the exam application... It is totally unacceptable! But the application itself is quite old, I guess - the interface looked like good ol' Win 3.11
There were A LOT of questions concerning the new topics! If you know the 1.4 stuff well, but only know the basics of 1.5, you will probably fail. In this case, you should probably go for the 1.4 version. But for those who have decided to take the 1.5 exam - I strongly advise everyone to get a good grip of the new things - generics, enums, variable arguments to methods etc... I didnt study them enough and this is reflected in my score...
Unfortunately, I cannot give you examples of questions that I got on the real exam, although I can assure you there are some really tricky ones. When I was doing mock-exams and came across a tricky question, I always thought that this is too tricky/difficult to be on the real exam. Boy, was I wrong The authors should be ashamed of themselves for including such questions on the real exam!
Finally - I have only less than a year of "real" Java experience. I have coded some Java before though, when I was studying at the university. I used approx. 2 months of preparing, mostly studying at home for an hour or so in the evenings.
Good luck, and I'd be glad to answer any questions!