i've been browsing the forums after a recommendation from a friend, but haven't really posted. just wanted to add my feedback regarding knewton.
i studied on my own for the gmat for several months, using
the official guide, kaplan, kaplan 800, and several
manhattan gmat books, and initially got a 700. i wanted to get a little higher to improve my chances at a top tier school, so i decided to take it again. i came across knewton and its 50 point guarantee, so i decided to go for it. i honestly don't think i learned all that much from having attended the sessions, but the extra practice problems were helpful just to get more exposure to problems and to work on my timing. as has already been mentioned, the scoring for the practice exams are a bit peculiar, but nonetheless were good practice. in the end, i ended up getting a 730, which i hope will be good enough to get me into a top school when i do actually apply.
since i didn't improve my score by 50 points, i'll be getting a refund from knewton for my course. looking back on the course itself, the lessons themselves weren't all too helpful, but the additional drills and exercises were. since it's an online program, it also helps that i was able to do the problems at work on my computer during down time. overall, if i were to do it again, i'd sign up for knewton- if you already have a decent score on a previous gmat sitting, it's basically a good way to hedge your bets and also get additional practice preparation in for the next exam.
hope this helped, and if anyone has any specific question/s please let me know.