it take for me 3 months of preparation, with 1h per day at work and 4 hours per day at home to pass this exam with 91%
i read Head First Servlet and Jsp of Bryan Basham, Katty sierra & Bert Bates and specs Servlet 3.0 and finally the questions of http://exam.piotrnowicki.com/ (that help me lot !!! to understand the concept of the new features of servlet 3.0, and i bought also the exam from the enthuware web site , these guys are awesome !!! trust me buying the mock exam form these guys http://enthuware.com/ is mandatory and you will not regret !!!
Finnaly big thanks for enthuware and katty sierra and Piotr Nowicki !!!