I took the Kaplan course from mid-July to mid-August. Here's a debriefing of my experience and recommendations. I'd like to warn you all that I may not remember all of the details. Anyway, I'll break it down by category.
Argument Essay: I thought that Kaplan did a good job. They taught you how to structure the essays. Included in the structure is a paragraph where you are supposed to state how to strengthen the argument. I don't remember if it was the book or the instructor but he basically gave a "cheat sheet" answer to it. Just say, that research is needed. Without that knowledge I might be racking my brain. It's nice to never have to worry about that particular paragraph. You're also taught you how these essays are similar to critical reasoning. Because of that knowledge I came to a conclusion that the vast majority of these essays have two fallacies, one of causality and one of representativeness (more on this later). I used these two fallacies in my last half dozen or so argument essays. Interestingly I didn't do so in the real GMAT, because I felt like the GMAT established causality. I used another fallacy (a weaker one).
Opinion Essay: You also get structure here. I didn't feel like this is taught as well. However, I think that's because this essay is less structured. I actually dislike this lack of structure as I feel like I've free styled the essay too much. I've been seriously satisfied with these essays when I knew the topic well. I was lucky enough to get a topic I knew well for the GMAT. But my biases shouldn't be held against Kaplan. I don't know how much they can teach you beyond the structure which they did.
Problem Solving: They went over every category that you'll find on the test. Obviously, not every type of question you'd get (but I don't think any service would). That said, I thought that the
Manhattan GMAT was more in depth. I think that the Word Translations in the
Manhattan GMAT is superior to Kaplan. For example, I would always struggle with rate problems and the
Manhattan GMAT's RTD/RTW table approach really helped. I feel like the
Manhattan GMAT also did a better job of explaining permutations and combinations. The anagram approach of the
MGMAT can be very helpful. For some reason I didn't use it though, but I think it can be very helpful. There was actually an "advanced" question in Kaplan that can be solved with the anagram method, but the actual method is not taught. They also showed how to do many more types of of the problems (I didn't really use them much in practice tests). The
MGMAT also went into a little more depth for the Numbers properties. I won't say that the
MGMAT gave me a lot more information, but definitely did. I still wish that both sources would give me more information for difficult number properties. I got lost and spent a lot of time on a difficult numbers property question on a real GMAT and ended up guessing. For Geometry I think that Kaplan did a good job. The
MGMAT did show me how to do a few different question that gave me trouble on a practice Kaplan test that Kaplan never showed me how to do. However Kaplan did go over geometric figures that are made up of 2 or more figures. The
MGMAT did not.
Data Sufficiency: I didn't like Kaplan's approach at first. However, it's also the
MGMAT's approach. The approach is mostly rewriting the question stem and the statements. I got the hang of it and for the last 4 GMATs did pretty well on the data sufficiency (11/15, 11/15, 12/15, and 11/15 and usually getting only the tougher ones wrong). So yes Kaplan (and the
MGMAT) helped.
Sentence Correction: They went over all of the categories. I guess it sort of helped. I did notice grammatical mistakes rather than just go by what sounds good. However I was still pretty erratic with these. The
MGMAT was much more in depth. It helped with with present and past perfect, for example more than Kaplan. However, I'm not sure how much the
MGMAT book helped. I read it at the end of my studying. In fact I postponed the test because I felt that my verbal was weak and bought this book and the critical reasoning
MGMAT book. I took 2 practice Kaplan CATs. The first test that I took I got 10/13 right. In fact, I went over the 3 questions and feel that I should have gotten 2 of the 3 that I got wrong right based on my knowledge (the 3rd one was tougher). However on my next Kaplan CAT I only got 8 right. I don't know how many I got right on my real GMAT. I didn't feel in great control of my sentence correction. However I got a good score on verbal (41) so I couldn't have done too poorly. In conclusion, I think that Kaplan and the
MGMAT have helped me diagnose some problems. Overall I'd say I improved. However, I wasn't overly consistent. That's probably my fault as much as anything. As I said Kaplan (and the
MGMAT) did help me diagnose problems, I think they're both helpful.
Critical reasoning: I thought it helped me when I did well on Critical Reasoning. By that I mean, that for some reason it was a weakness of mine, but when I did well I think Kaplan strategy helped. The evidence/assumption/conclusion and also the causality/representativeness did help. The latter helped me more in the argument essay though. Causality for some reason was a problem for me to diagnose. I think that Kaplan may be better than the
MGMAT at this. I thought the Critical Reasoning
MGMAT book was good mostly for practice. I also thought that their practice problems were uncharacteristically easy.
Reading Comp: Not a fan of this section. Kaplan helped me refine my note taking skills and especially with global questions. They teach a lot. They teach Topic Scope, and Purpose. I never wrote all of that out, but did have purpose and author's tone in mind, which helped with global questions. They also teach question types. I don't know how much that helped me, once again mostly global questions and inference questions it helped me with a little too.
MGMAT, I didn't even finish the book, it seemed very similar to the Kaplan strategies. That said, I still say that reading comp depends mostly on the passage. If it's a tough natural science passage, I'm having trouble either way. However I was fortunate to get easy reading comp passages and questions on the real GMAT. Saved a lot of time and gave me points (I don't know for sure, but I assume). I don't know if they really teach you how to attack some of the most difficult passages. They do say to skip the details, I wouldn't say that it works.
Tests: I thought that all of the CATs were pretty representative. The diagnostic is not a CAT and is actually MUCH easier than that the real GMAT. It's weird since that's what they base their money back guarantee on. However, on just my second test I got a 660 and since then I took 12 tests including the real thing. I got a 660 or higher 4 times. The next CAT that I took I got a 590 in, that was the second GMATPrep. The CAT after that, my first Kaplan CAT I got a 510 in. I also had the highest percentage of any test that I took on the Diag (don't know about the real GMAT though). I guess since it wasn't a CAT I didn't get a score representative of what I would get on a CAT. The other tests were a lot closer in difficulty. I thought from all that I read that the GMAT would be easier than Kaplan. Let me tell you, maybe the CD ROM is different. But that's definitely not the case. The Quant was as difficult as any Kaplan Quant and I don't think that my nerves played that much of a role. I think I was answering questions decently, but spent way too much time on them and had to guess the last 10 or so. The verbal was easier to me than most verbal in Kaplan CATs, especially the reading comp, which I thought was pretty easy (both passages and questions). Critical reasoning was easier to me than most Kaplan CATs. Sentence Corrections was on par. Also important to note, their scoring is off. I had a Q48 and V45 on one test and Q47 and V45 on another, they both got me 710. I've seen people here with Q48 and V41 and Q47 and V41, and they got something like a 720. On the other end of the spectrum, I once got 88th percentile quant (49) and 48th percentile verbal (28 or 29) and got a 660. I think from my experience here, that may have been a tad bit generous.
Resources: It's good to know where your weaknesses are, so that's positive. I think that Quiz Bank, despite having difficulty levels, is not representative of even the Kaplan CATs. An identical question to a first question in verbal (medium level) was difficult in the Quiz Bank.
Instructors: I had 1 regular one and 2 subs. 1 of the subs was mediocre and wasn't a great teacher and bored me. The other sub was more interesting and was pretty good. Though I asked him a question in grammar that wasn't in the curriculum and he didn't know. The regular was awesome. Always spent time with me after class. Always answered my e-mails, even after class was over. He was the best part of Kaplan for me.
I think that's it, that was a mouthful! Any questions, let me know!