Hi

I would like to first remind you that GMAT is a CAT(Computer Adaptive Test), so once you perform well, you start facing tough questions.
While OG is written keeping in mind, a general view about the test takers. So as you start answering questions correctly, you definitely face tough questions. Thus the difficulty level of the questions you face depends on your performance.

i did many OG 11 questions, and they're definitely too easy. on the flip side, manhattan gmat quant section is much harder than the actual gmat. the most accurate representation i found were the gmatprep tests. unfortunately, they don't give you explanations (although if you search the forums, most of the questions have been answered/ explained already).

i would recommend you study using practice tests from MGMAT. take the tests, then focus on the ones you got wrong and study that material more in depth. that way, even though the material is harder, you will learn to work more quickly to finish the section.

Thanks gmat740 and shadowsjc

I have approx 20 days before my test. I'm not as worried about the Verbal section as I'm about Quant. I didn't want to refer to too many books and have stuck to OG11, OG-Quant, OG-Verbal and Kaplan 800. As far as practice tests go, I've GMAT Prep, Kaplan CD, PowerPrep, A few Princeton Reviews (not yet attempted), Barrons and Nova. The last two appear useless and error-ridden. I also have registered for the free Manhattan test. I've been concentrating on GMATPrep and Kaplan till date. I thought PowerPrep to be a little too generous in its scoring. I've solved the OGs and Kaplan 800 multiple times, which is why perhaps they appear easy to me. I get shot down by the Quant on GMATPrep. The highest I've got on GMATPrep is a 680. Highest on Kaplan CD test is a 600.

If I can manage a good score on Quant (especially on DS) then hopefully I can crack the 700 barrier. As of now, Ive decided to take a practice test on alternate days, and work on weak areas on the other days.

i may be in the minority here, but i don't advocate taking the gmatprep more than twice. after that, you're bound to get repeat questions, and it could affect your score.

i don't know how good the explanations are on the other full length tests you mentioned, but with 20 days to go, it's more than enough time to purchase an MGMAT subject book and get the free 6 tests that come with it. their explanations are great, and like i said before even though the quant is harder than the actual test, it will serve as excellent practice.

just to give you an idea, i picked up my copy of my mgmat book just 1 week before my test. i didnt even get a chance to go through all the included practice exams, but it definitely helped alot.

@shadowsjc hey wait a minute! did u just say I could get the 6 MGMT CATs just by purchasing one of their books?? WoooHooo!

yes that's correct. that's why buying one of their books is such a great value and i recommend it to everyone on the forums.