Today I passed SCWCD 6 with 96% (also passed Java Standard Edition 6 Programmer with 98%) I am very happy I worked hard.
I just want to share my experience hoping that it helps.
I have a lot of experience in programming including Object Oriented, but I didn't work with java before. The java 6 wasn't that bad for the preparation
but for SCWCD 6 I didn't know from where to start. I couldn't find a book, finally I bought murach's Java Servlets and JSP 2nd edition. I read it twice I found that it was a good start
but not enough especially for the Servlet 3.0 part. I also bought ENTHWARE exams (good quality and not expensive) and that was really a good choice the answers are very clear and it also refers to Servlet 3.0 spec for details.
ENTHWARE are more difficult than the real exam and helps you master the concepts.