I took up the 4GMAT course in Anna nagar. I would'nt say it was Extremely helpful , but if your looking for something like over 650+ , this just is'nt enough. If u already know about the GMAT and its intricacies - you would find this course a basic start up . The course is for ppl who just blindly come in with the thought of writing the GMAT to get any idea as to what this exam is about, advanced test takers would not find this very helpful. Yes, u do learn alot . The math faculty are excellent preferrably Rajesh. Simply amazing ! . As far as verbal is concerned, Swetha does a good job. You will find it good, but just not enough. Trust me, you would have to spend lots of your time other than working on the stuff they provide. The quant material provided is outstanding. Attend a verbal class, probably SC -1 or CR-1 .. don't sit in an SC-2 or CR-2 class. You can attend any Quant class coz its a different topic every week with a different instructor
My take - If you already know your calibre , just buy the quant books and work on them . Verbal - you will need the Manhattan SC, Powerscore CR
and any RC source .
Disadvantage - shuffling of quant instructors. I personally found it tough to adapt to their teaching styles.. probably 10-15 mins. This is crucial, because they go about the basics. Attend a session, you can decide then
Do let me know if u want more details, i am active on this site.