Passed the GIAC 2700 exam on Saturday with a 81.33 score, and used a little over one hour.  This test was much closer to the CISSP and CISA than any others in the WGU MSISA program, for sure.
After much thought, I did the open-book material I took in the exam a little different than Agent47 here:  
http://www.techexams.net/forums/sans-institute-giac-certifications/88987-passed-giac-g2700-exam-today.html  Although I am grateful to him for giving me ideas on what to research and be familar with.
Maybe because my brain processes information differently, I had a hard time making 'notes' in the same manner, so i wound up taking two binders into the exam - one with the verbiage of 27001, 27002, and 27005, and another with more detailed, topic specific information such as wikipedia articles, a few technote pages, etc.  (I don't know if listing everything I took in my binders is appropriate or not; if a mod permits, I will make a list.)
On the practice exams, I used my binders maybe a total of 10 questions out of the 150, and scored 74 and 93.  On the actual exam, maybe paranoia played a factor, but there were quite a few that required me to look up specific things in the standards, and I probably would not have passed without those, for sure.  Probably 40-50% I had to confirm.  Put all your docs in plastic sleeves (it takes forever but is worth it!) and I grouped my printed topics into sections (like legal, project management, risk management, etc) which was invaluable in locating information quickly.
I honestly didn't study a whole lot; I DID read 27001 and most of 27002 (it gets old after a while) and 27001 was actually far more useful for me.  I didn't really use any outside resources other than the controls, and what I had in my binders, but I also have CISSP and CISA certs, and a fair amount of experience, especially in C&A (some of my previous jobs included bank auditor, and then DIACAP consultant for the USAF.)  I also got some ideas for what to have in the binder from 
Passing the G2700 ISO 27001/27002 certification: What Materials you will need for the Exam., and I had far more than what I needed, but I wanted to be well-prepared.
As far as certification tests go, this is one of the more challenging.  It would be a helluva lot hard if they made it longer; it is quite taxing mentally, much like the CISSP or CISA.