Their is no need for the Gouge. The books are good, the classes are taught well. Alot of the gouge is wrong, alot of it is old, its kind of a waste to weed through it. If you are not 100% on the material, the gouge can easily throw you off. Atleast 10 questions on the API practice tests were wrong, for instance.
That being said, I looked at the test to get a feel for how much I knew.. but that was a last day sort of event, nothing that happened early on in my study process.
My average was around 95, so I am not an absolute athority here, but, Live by the Gouge, die by the Gouge.