"Took the GMAT on May 3rd 2006 and scored a 750 (99th percentile). I couldn't have done it without Wizako(4GMAT)".
I had joined their classes around January 2006 after a two week long research of most GMAT coaching centres in Chennai, but I didn't really start preparing till a month before the exam. Till then, I was focusing on Kaplan and Princeton and all the other preparatory guides available on the market, limiting my Wizako experience to interaction during class hours. Those three months were a criminal waste of time.
At first, I was misled by these guides into thinking that the GMAT wasn't really all that tough. It was only when I started becoming active on some internet forums - urch and sentencecorrection to name a few - that I realized how tough the GMAT really was and how much effort I needed to put in to attain my goal of 700+. Understandably, I was quite upset at having wasted nearly 3 months on those material; With three weeks left for the GMAT I realized I really needed to ramp up my preparation. Thus began my actual GMAT preparation.
The first thing I did was take up Wizako material. With time being of the essence, I decided to revise the complete notes and formulae instead of attempting every exercise from the text. Having been regular to class, my comprehensive notes already encompassed a subset of what was in the text/e-books (The exercises were left for us to do at our own pace after class hours). After having battled with a number of tough math questions on the forums, I realized that all the important questions and techniques of each 'type' of question under a section had already been discussed in class.
I strengthened verbal by using the strategies and techniques I learnt in the verbal classes of Wizako and practicing on a gamut of material that I had sieved from online forums. These were instrumental in significantly improving my accuracy. I went from a 710 (After working on the Official Guide) to a 760 on the GMATprep practice software and I attribute that 50-point increase solely to Wizako.
I think information is the key to a high score. The better informed you are, the better prepared you are. The only materials that are representative of the types and difficulty level of the questions you will encounter in the actual GMAT are Wizako and the online forums. Besides these, you would do well to supplement your preparation with the Official Guide and Manhattan Sentence Correction (for gaining a solid foundation in grammar).
If there's one piece of advice I would like to give to anyone planning on taking the GMAT, it's this - Stay away from the 'regular' GMAT preparatory guides. Relying solely on them for the GMAT is like sending a lamb to the slaughterhouse. The content is much too easy, quite sub-standard compared with the actual GMAT, and it only serves to give you overconfidence and that could be your undoing on test day! Instead, practice on the Official Guide to get the hang of it and then fine-tune your preparation by investing in the exhaustive Math repository of Wizako and by culling out verbal material from the various online forums.
Only Wizako gives you the tools to prepare for the quantitative section of the GMAT; No other GMAT preparatory material even comes close. At first, I had thought it was too comprehensive and neglected to make full use of it, but I took it up again three weeks before the actual GMAT. After taking the GMAT, I think without this degree of preparation I would have been at a total loss on test day. Under Pearson, the quantitative section seems to have become tougher and it gives equal weightage to all sections - Number theory, probability, permutation/combinations, geometry, equations, mixtures ... And that's just scratching the surface! If you are unable to attend the classroom course, purchase the e-books or math material at least.
A final word of advice - If you decide to invest your time and money in a coaching centre, please make sure to take time out to visit the centre and speak to the directors. Higher cost does not equal better coaching/better material/more hours/additional MBA-related services/more tests. In fact some of the high-end centres I visited before settling on Wizako seemed more like revenue generating organizations than coaching centres. Ultimately, if the centre is reluctant to divulge the contact details of the faculty/current students or don't discuss any material other than their proprietary material in class, you might as well prepare by yourself. It pays to join a centre with a well-stocked library and helpful faculty who will be willing to guide you on any MBA-related issues even if strictly speaking, it does not fall under their purview.
One reason for my high score is that long after the completion of my classroom course, I kept pestering my instructor with math problems (hauled from other books/forums) I had difficulty with. He was very helpful and even offered to let me sit in for one class on inequalities that he was taking specifically for another batch of students appearing for a different, more math-rigorous exam. Having that kind of support is crucial to a 700+ score. Ultimately, whether you decide to go in for the classroom course or settle for the Math material alone, if you are looking for that little extra to give you that much-needed edge, content-wise and otherwise, Wizako would be instrumental in getting you a higher score.