I just got through taking the GCCC exam and the actual exam was much harder than both practice test. The course itself was a lot better than what I expected. My SANs instructor did an incredible job explaining the importance of each control and how to tie it to any organization. The exam itself is different than most SANs exam in the sense that you have to understand the concept and not just rely on the index. I ended up only using my index about twice for my exam. 
During the week of instruction, I had read all six books and built my index as I went. I’m a huge fan of tabbing out specific sections in my books and I printed out a page with a list of controls. This helped finding the controls so much easier during the exam. If you take the time to read and build your notes tailored to you then you’ll do fine. However, there are some questions that I had no idea as to where they were located in the books. If anyone has any questions, please feel free to ask.