You should. Heres why. I have been preparing for this exam for the past two and a half months and I have spent most of my time working on quant. I have taken a few gmatprep tests and I have scored a 43, 39, and just now a 41. I scored a 45 on the mgmat quant tests. Everyone talks about how mgmat test is harder than gmatprep. This may be true when your dealing with 600-700 level questions but the upper end mgmat quant questions are way more difficult than those found in the materials distributed by gmac. What I am trying to say is I have gotten very good at handling most of the questions the gmat can dish out, yet I'm clueless on about 5-6 per exam.

@ Sallywoo - Yes, you should. But do not put a lot of time into it or stress about it. I am not shooting for a 700 either and have been told that any perm/comb on there will be pretty straight forward, if I see any at all. It is good to know how to do the problems. But again, the bulk of what you'll (probably) see is Algebra and the like.

Also, just because you got 1 or 2 wrong in a one topic (perm/comb) does not mean you will do poorly. You could be getting difficult DS or Algebra questions correct.

Hope that helps.

i'd like to thank both of you for the replies! so i'll make sure not to spend too much time on the topic, but to understand the fundamentals. that's very helpful!