i bought the prep book, and I took the first practice test, and it freaked me out. it was way more difficult than any other practice test. I personally wouldn't recommend it. the difficulty wasn't worth the practice.
The gold standard book itself is really useful. Not too detail oriented...(there's nothing on magnetism though, but mcat pearls can supplement that), but it forces you to focus on the general underlying concepts, which is invaluable come test time.
I used the kaplan materials too...and once i got through those, seeing the material presented by the gold standard helped consolidate everything i had learned. The practice tests are great, and the verbal is infinitely better than kaplan (plus it's harder than the real deal, but harder in the right way).
The audio stuff and video lectures are completely useless though. Don't waste your time or money on those. But i love the way the material is presented in the book...and my practice scores surged when i switched to studying the gold standard.