I agree. I did the subjects in the qbook that I felt the least prepared for, and when I got to the exam (June 27) I was surprised to see a few questions that were eerily similar to what I had covered.
That being said...USMLEworld is your best bet hands down in my opinion. Practice doing blocks of 20 as fast as you can go and you will be surprised that you don't do terribly. It's great to get 90%+ on a set of q's, but if you can get 75's and have 10-15 min left over I think it's better prep.
Doing that with usmleworld helped me finish a block of 50 on the exam with half an hour to go!
Good luck!