Ahh, yes!! Just my kind of topic! If you really don't feel prepared, and are reasonably confident (be honest with yourself here) that you can score better than you are on the practice tests, I would wait to take the test in August. I had this exact same problem -- I had studied for the April '99 MCAT, but I was taking a full course load as well. Thus, I didn't study for the MCAT nearly as much as I thought I could have, and I didn't feel comfortable with the practice test scores I was getting -- I really honestly believed I could do better (mostly because I never saw any real improvement in my scores). Then, I couldn't fall asleep at night the week before the MCAT -- it was wreaking havoc with my life. Four days before the test, I decided not to take it, against the advice of nearly 80-90% of the people I spoke with (you've already put so much time into it, etc.) I AM SO GLAD I MADE THAT DECISION!!! Ultimately, it made me delay applying an extra year, but it was still a good decision for me. I took the MCAT the next April and did much better with the extra time to study. Plus, I feel like the extra time off definitely helped make me a better applicant.
If you really honestly feel unprepared, and honestly think you could do better, I would suggest taking it later.
[This message has been edited by lilycat (edited April 05, 2001).]