hi... i have finished the jamboree live classes from gurgaon. But am yet to take gmat test. What i feel is alot depends on after the classes are done, how much are you taking leverage of the faculty with doubt sessions and customised plans. there material is exhaustive covers OG, beral and quant review. Most of the questions that i see on gmatclub are there in their material. Rest alot depends on faculty. My english exp with faculty is bad but i really like the videos they have on their portal.
please do let me know, if you find someone who has already appeared for GMAT. i would definitely want to know how much they scored and how did they go about it.