I think i have always been strong in Quant. and after giving GMAT Twice i knew i will do well on Quant. , the only thing different this time that i was aiming for q50/51.I knew this will increase my score by 10-20 points. Unfortuantely things didn't go as planned .

this has happened more often than not in my life.....Anyways coming back to your question.
I prepared quant. from MGMAT 5 books (solved all questions and marked the incorrect ones) and then i used to try them again and yes i solved all the OG questions (...same strategy) and ofcourse i gave all MGMAT CATS.The OG questions are below average level and few MGMAT Cat questions are above the average level.
Again I will say that GMAT Prep questions actually reflect the kind of questions that appear on the real GMAT , but dont use GMAT Prep questions as practice questions , give the GMAT Prep when u think you are ready for GMAT.Your score on GMAT Prep will reflect your score on the actual GMAT.Of course you can always redownload the GMAT Prep software and give this exam again for new questions !!!!!
The best books are MGMAT Quant. guides , if anyone really wants to score well on the GMAT , you have to go thru these guides , practice all questions and learn all concepts.The concepts are basic but most of us have completed our schools few years ago so its imp. to go thru these concepts again.
Ya !!! I forgot to mention i also gave the GMAT Club Tests (Sorry guys!!!!!) , i think these tests are excellent source for practice.These tests are a bit tougher than the Quant. section on GMAT , so dont get disappointed if u get a low score.
My prep Strategy
1) MGMAT Guides (Solve all questions)
2) OG 11 ,12 (Solve all questions)
3) Parallely Start giving GMAT Club Tests (If not all give a couple of GMAT Club Tests)
4) Give MGMAT CATS (All 6)
5) GMAT Prep CATS (Final showdown)...
Best of luck !!!!!!!