Here were my practice CATs:
Q/V/Score

Princeton Review:
39/41/650
39/36/610
50/37/700

Manhattan Gmat:
42/34/640
46/39/700
40/32/590
44/35/650
40/38/650

Real score:
42/41/680, 86 percentile

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I found that the actual GMAT on test to day be pretty easy. There were a few questions that I rushed through and didn't spend time figuring out because I thought I was going to run out of time, even know I knew if I spend another minute I would have got the answer. I ended up finishing with like 10 minutes left in time. I think I would have gotten a 700 if I just paced myself better.

I don't know if I am going to retake the GMAT because I have a pretty solid GPA. I think that I could take the GMAT again and get a 700, but I really just don't think it will make a difference.

I encountered 0 probability, 0 combinatorics, and only 1 word problem on the entire exam. I feel like every other question was a quadratic or absolute value question.
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My advice: The forums are the best place to improve your score. Test prep companies are a waste of time. Buy the 8 MGMAT books and learn it all on your own.