Well, from my experience, dont expect quant and verbal in the actual test to be of OG level. It is surely of a higher level. I felt that quant quite reflected the GMATPrep's level. In verbal, RC and SC were okay, but CR was definitely tougher than OG, much closer to the LSAT-CR's difficulty level.
Dont let OG's level guide your preparedness. ITs always good to practice some tougher questions!