It's been at least a couple of years since we "got" to take brainbench tests at work, but here's my recollection in general (since I didn't take this specific exam):
The difficulty of brainbench exams varies, but none of the exams I took were as difficult as say
SCJP exam. Some junior
java developers did fail java exams, though. If you are not familiar with the difficulty of SCJP, even experienced java developers that don't study specifically for the exam may fail.
The exams were open book so an important part of exam prep is gathering materials (books or internet bookmarks or search engines) on the key topics. A certain amount of time is allowed for each question, if you don't know the answer off the top of your head you need to be able to find an answer quickly.
I'm not saying not to study or review the material, you need a certain level of understanding to know where to find the answers or what terms to use when searching...unless you are just really good at using tools like google.
Good Luck!
[ November 25, 2006: Message edited by: Carol Enderlin ]