YES--its definitely worth it, especially if you don't know your strengths and weaknesses are in GMAT quant. The quiz gives ou 24 questions to solve in abourt 42 min (I think). Once you finish, you get a score range and then the system breaks down each question type (DS and PS) and the question material (word problems, algebra, arithmetic, etc) and where you score among these topics--scores range from Below average to excellent. I think after the 3rd quiz, the questions repeat themselves.

By the way, I didn't see many questions that were identical to the OG books but if you've been studying the GMAT long enough, you know that the materials tested (multiples, factors, percents, probability, etc) get tested repeatedly, just the numbers change

I highly recommend taking AT LEAST 1! Good luck!