I have been lurking on the boards for a couple of months, and found other people's experiences with the GMAT very helpful. I hope this post helps too!
Background
As you may have guessed from my user-name, I'm a lawyer. I wrote the LSAT in 1999 (oof - can it really have been that long ago?) and used only the Princeton Review book to study with. My score was good (90-something percentile) and standardized tests have always been a strength of mine. My experience with the GMAT was far more humbling.
After studying with the Princeton Review GMAT book and the Official Guide for a few weeks, I took GMATPREP 1 and got a score of 720 (94th percentile), Q44 (68th percentile) and V46 (99th percentile). I figured if I spent the next couple of weeks brushing up on math, the test would be no problem.
First GMAT
I wrote my first GMAT in August and got a score of 650 (79th percentile overall), Q36 (43rd percentile) and V42 (95th percentile), a full 70 points behind my one and only practice test. I beat myself up for a day, and then decided that it wasn't over and that I would write again.
My target was to apply to INSEAD, so I knew I wanted a better score to improve my chances - ideally at least a 700 (my research indicates that 650 is at the very low end of what INSEAD expects, though not completely out of the range). Also, I knew that INSEAD wants balanced Q and V scores, and that my scores were anything but. THe 4.5 AWA was also a blow, given that I write and argue for a living.
I needed a new plan of action, one that would ensure that I got all of those grade 10 math skills back in my head. I had always been a good math student, but it had been many years since I had had to use that part of my brain.
Study Plan
Since my goal was a 700, I decided to go with the Knewton course, figuring that either I got my 700, or the course was free. Either way, I'm no worse off. I signed up at the beginning of September with a "Share the Love" code, so the cost was $490.
Let me tell you - it was the best money I could have spent. Everyone's brains work differently, but for me, Knewton was exactly what I needed. I needed a plan (which Knewton's syllabus provided) and a sense of where my gaps were (which Knewton's progress reports provided). I loved the structure of assessments/homework/re-assessments. I loved the teachers: I had primarily Chris Wu and James Boo, but did some of the classes by way of archive. They were all good, though the live classes were better because you can ask questions, participate in the polls, etc. It really feels like you're right there with them, and that they care about your success. They do combinations/probability in one of the last math classes. I was confused and getting behind, and one of the TA's noticed that I wasn't getting many answers right. He privately messaged me and got me back up to speed.
Let me tell you - the idea that I needed extra help with the GMAT was humbling for me - I really thought I should have been able to do it on my own. But it was worth it.
Practice Test Scores
There are 5 CATs through the Knewton course. I took one diagnostic test before the course started and scored 590: Q31 V42. In all honesty, I didn't really put my all into that test and was just trying to see how their system worked (at the time, I was on a free trial). I also knew that I could use my official GMAT score as my baseline for the 50 point guarantee.
Week 5 of the course I took the second Knewton CAT and scored 700: Q39 V49. This was a good sign, as some big math concepts, including geometry, had not yet been covered.
The week before my second test I took the third Knewton CAT and scored 570: Q35 V36. I don't know what was going with me that day. I think I went into the test with the attitude of just getting it over with (as you have to complete all the CATs before your GMAT in order to receive the guarantee) but my score scared me enought into taking my last week of prep very seriously.
I wrote my GMAT on a Monday morning (yesterday, specifically). So I used the weekend before do do more practice tests and brush up on any concepts I needed help with - Knewton's concept queue was really good for this. Saturday I took GMATPREP 1 again and scored 730 (unfortunately, I seem to have misplaced the breakdown of this score). I knew that there were a few repeated questions from when I had written it in August, so took this score with a grain of salt.
That same day, I took Knewton CAT no. 4 and scored 650: Q36 V45.
I reviewed some more math that night (as clearly that was the area in which I was lacking) and took 2 more tests the next day. On GMATPREP 2 I scored 710: Q42 V45 and on Knewton no. 5 I scored 680: Q39 V45.
Other than the Knewton homework and assessments, and the 2 GMATPREP test, I did no further studying. I had gone through the official guide questions in preparation for my first test, so my book was all scribbled in already.
GMAT No. 2
I went into the exam the next day with 2 goals: score 40 or higher in quant and score 700 overall.
I had already taken one GMAT at this testing facility, so knew what to expect. I wrote at 8am (morning isn't usually my best time of day) but preferred it to my first test time, which was 4pm (and allowed me to stew about it all day).
AWA was fine - I much prefer the analysis of an argument to analysis of an issue essays. I finshed about 10 minutes early and took a 5 minute break.
After the break, Quant felt good - a welcome surprise from the first time. I recognized more of the question types, knew when and how to guess, knew how to properly test cases (a big weakness of mine). I had just under 2 minutes for the last question, thought I would have been able to answer with more time, but made an educated guess just before time ran out. One of the things Knewton really helped me with was timing - I noticed a big improvement. I spent too much time on the first question (I really wanted to start out right!) but caught up quickly.
I took another 5 minute break and, relieved that Quant was done, started into Verbal. Verbal had always been a strength, but I had a tendancy to rush through and finish very early - often with more than 25 minutes left (I'm an extremely fast reader). I deliberately tried to slow myself down. It felt a bit tricky actually, which is not what I was used to.
When I finished, I took a deep breath before asking to report my score and up flashed 690. Now, it wasn't the 700 I was looking for, but it was pretty close. Moreover, my Quant score had gone from 36 (43rd percentile) to 43 (66th percentile)! For you math geniuses, this may not seem like a huge improvement, but for me to have beat my goal of 40 by 3 points was a huge feeling of accomplishment. I was slightly annoyed by my verbal score of 41, given that I had routinely scored much higher than that in practice tests, but ultimately decided that it's not worth fretting about.
My overall percentile was 88 - a pretty big increase from the 79th I had gotten with my 650. My quant score went from 36 to 43, a percentile increase of 23 points (!!). My verbal score went down by 1 and percentile dropped 3 points to 92nd. Part of me (a very small part) wants to write again to get that verbal score up to where it should be, but I think my husband would kill me if I spent even one more day obsessing over this exam.
Overall, however, I'm very pleased and relieved. My scores are far more balanced, and put me in a much better position with respect to my application. I attribute my whole gain in quant to Knewton, and my slight loss in Verbal entirely to me. I think after Quant was done I was so relieved that I may not have been as focussed as I should have been. I may have also done too many practice tests right before the real thing and was experiencing a bit of GMAT fatigue.
I would be happy to answer any questions anyone has, about the Knewton course or otherwise. Again, I can't thank Knewton enough! I almost feel bad about asking for a refund on the $490 spent because I think they upheld their part of the bargain (I haven't contacted them yet about the process). Chris and James - if you're out there - thank you!