I got my certification and am super happy that I passed. While YMMV, I believe that people describing their study methods helped me considerably in how I determined that I was ready to take the exam.
The company I work for pays for time and materials if you choose to get a beneficial certification. I was also on the bench, between clients, which is why I had the time to study for this at work. It took me 6 weeks @ 40 hours a week of studying to feel prepaired for this exam.
Since I had ~3 years of Java technology industry experience, I felt pretty confident that I could knock out this test after studying for a minimum of 2 weeks and a maximum of 4 weeks. For me, this assumption was wrong. I spent the first week going over the exam objective from the Oracle web site, it didn't seem too difficult at the time.
I then found this forum (which is a great resource) and found out about the Enthuware test suite (I highly recommend this). For the first test, I had a score of 42%, same with the second, and the third test was about the same. These tests helped me realize that I was no where near ready to take this test.
I then picked up Mala Gupta's OCA Java SE 7 Certification Guide and studied this for about 3-4 weeks, and using the JavaDocs for memorizing some of the APIs for the String, StringBuilder, String Buffer, and the primitive wrapper classes.
After I got through Mala Gupta's guide and took the final test (my final score was about ~65%) I then went back and started taking the Enthuware tests again, tests 3,4, and 5. I was getting scores around ~65% and spent more time understanding why I missed questions. Because I read Mala Gupta's guide, I was able to easily understand why I missed questions, then used the guide, and other resources to fill in my knowledge gaps.
After I was done with the 5 practice tests, I was wondering how I felt about my knowledge level and I took the objective tests which are also provided in the Enthuware suite. I averaged 85% on those questions and felt very confident about my answering ability. Upon seeing the answers for my missed questions I immediately knew why I got them wrong. This is when I felt ready for the exam, took it the very next day and passed.
For those reading these forums and looking for answers, please remember that depending on your situation, this may be too much studying, or it might not be enough studying, but this is was worked for me. Your milage may very.