Ok, I promised to get back on this after my
SCJP attempt. Yes, Sun's ePractice example exams are very close in form to the actual exam. Some of the real exam questions are a little more difficult than the practice exams, but with a little extra turbocharged thought applied to them, they're crackable.
I had more problems with the noisy "class room" environment in which I had to take the exam, than with the questions. It's difficult to concentrate on those nasty do-while, if, break, continue, post/pre increment "guess what this does" type of questions when there's too much activity in the examination room.
Oh yes, the cost. US$ 75 is about 40% of the local price of the exam for me, I was prepared to pay that for the confidence
boost I obtained in the 5 days prior to the exam. It was also a bit like an insurance premium, US$ 75 is less than the cost of a retake.
If you are on a low budget, then Marcus Green's mocks and those in the Sierra/Bates book are adequate after reading and digesting a "serious" book like "The Java Programming Language" by Gosling, et al.
My recommendation is "Take your time, don't cram it, digest it".