Congrats Dan! Oh wait, I'm the friend who studied with you and I already did that. I will at least second his opinion about the JQ+ exams. They were an excellant gauge for telling us we were ready, and they pretty accurately reflected the "flavor" of the actual test.
My background is as a technical lead/designer/programmer having used Powerbuilder for the last five years (and toying with various structured languages before that).
Just so anyone doesn't get too cocky and think they'll automatically do 10-20% better than their JQ+ scores (like Dan), mine were more closely matched. My last four tests were in the 80's and I got an 86% on the actual certification exam. I finished the test with 25 minutes to spare (at which point I pressed "done", I had no desire to go over my answers and I don't want to see another test question for awhile
I at least started a little differently than Dan. Becoming interested in Java, I first went through the Que book "Java from Scratch" and built their application (starting in the first week of December). It was after that that Dan suggested certification to me and we hit the exam books heavily (very heavily mind you, we maybe did that portion in a month...but we put a LOT of time into it. Work was unusally slow in January and we did a lot of whiteboarding).
I tried to base most of my study by understanding the concepts involved and was hoping to be able to derive most of the answers I needed (Dan was on board with this as well). I guess I only mention this because a number of folks have brought it to my attention that these certificates were pure memorization and I've found it didn't have to be that way (ok, there is some, but concepts can take you a long way). I do not have the API memorized (not that that wouldn't help if you were very concerned about your final score).
I'll sum this up by saying I felt the whole thing was a rewarding experience. I love the fact that I have such a sound base knowledge in the language proper. I know others have written that the test should come later after more experience has been gained, but my feelings are that I can now freely focus on all the design aspects of the language.
Good luck to all those currently studying!