I would agree with Jim. The OG alone is a strong practice tool, but has 3 glaring weaknesses:
1) Explanations are poor. It doesn't teach concepts, but merely states facts (often by making big leaps).
2) For higher scorers who aim 710+ scores, the OG has too few really challenging questions. This is why people resort to studying out of LSAT papers for example.
3) Questions are not arranged by topic so it's difficult to devise an organized study program whereas you would focus on a specific topic until you master it before moving on. It's not easy to track how you're doing by topic (I don't mean question type)
As I pointed out in my debrief (
www.tinyurl.com/gmatpost) I have used the OG Companion from gmatfix specifically to address those weaknesses. It provides more detailed explanations to the OG11 quant questions so that helped me break the questions down to their essential parts. The Companion also has several advanced timed drills for high scorers, and it catalogs each question by topic and subtopic (for example, Geometry --> Triangles) and by difficulty level (200-400, 400-500, 500-600...)
There are of course other resources out there to help you address the weaknesses of the OG. MGMAT has a "challenge questions archive" and Kaplan has an 800 book (don't remember exact title). I would tell you more, but I don't know much about them.
In my opinion the bottom line is that the OG is necessary, but not sufficient to execute a thorough GMAT curriculum. It offers great practice, but doesn't
teach that well.
