Passed the SCJP 1.4 with 91%. I've been working with Java and J2EE for about 3 years but it still took me about 4 weeks to prepare, working evenings and weekends. I think my previous Java experience may have been more of a hinderence than a help, as I had picked up a lot of misunderstandings about how the language works and it took some time to rid myself of these.
I used the Sierra and Bates book extensively for my preparation and can't recommend it highly enough - some of the review questions they provided even came up on the actual exam !! Before using the book I was scoring about 50 - 60% in the mock exams, and after consistently over 90%.
In addition I took as many exams as I could - Maha Anna has provided a great list of free mock exams available on the web and consistently scoring highly in these did my confidence the world of good.
The hints and tips from other members of JavaRanch were valuable, in particular the list of most common pitfalls on the exam - I memorised this by rote !
One last thing, I didn't book my exam with Sun until I was scoring around 90% on all the mocks. I only did this because I wanted a good score on the SCJP to put on my CV.
Anyway onwards and upwards. SCWCD 1.4 is next (when it eventually comes out in the UK) and then the SCEA.
Thanks to JavaRanch, Kathy Sierra, Berta Bates and Maha Anna's mock exam list for helping an old timer like me, who hasn't been in school for over 10 years, pass the exam.