Wrote my first GMAT prep and got a 620. Was bit of a shock to me after practicing OG and the verbal and Quant review. FInally Took the gmat club subscription and started practicing sectionals. Was really impressed with the GMAT club's qustion bank. Though the exams are little tough compared to the Gmat preps and OG but in a way that's a good thing. You get to practice tough questions which eventualy helps you with the speed and accuracy. After practicing GMAT club's questions for few days, i finally wrote another GMATprep yesterday and got a 720. That's a 100 point jump and i was pretty surprised. All thanks to GMAT club. The questions in the Gmat club are all new questions that i haven't practiced before. I started from 44 in quant and 28 in verbal and reached 49 in quant and 40 in verbal. Still a long way to go as I'm aiming 750. Would recommend writing Quant sectionals and verbal quizes if you wanna jump your score up. Even the explanations for all the questions are pretty good. Would definitely recommend to a friend!!