is OG the one???

For me, it's hard to say that the OG is enough. I didn't use it for quant, I only used it for verbal. All the quant practice I had was answering questions on this forum. I've said it before: if you can explain a question in such a way that even a non-native speaker can understand, then you're basically there.

But I can say this: on the real thing, GMATprep-styled questions ruled the land! It was the statistics questions and the word problems that got me thinking a bit, so if indeed statistics is your weak spot, then I suggest you work on it. I saw something like 2 or 3 questions on stats! And again, they had this weird geometry problem that was solved using this special theorem that's literally called "a crow's beak" in my country. It involved a circle and tangets, but I'd forgotten the theorem so I just took an educated guess...

Most people can testify that the OG is not exactly all you need when trying to get a super-high score in quant, but that depends on your starting level. I didn't use it and still got a 50 in quant. In the end, I'd advise you to try and find weak points (whether you find them by practicing with the GMATprep software or with the OG, it's ultimately your choice) - and you already know one - and work on those. Maybe go back to basics by using your high school maths book?

But if you're looking for some tough GMAT-style problems, there's no easy way of finding them. While Kaplan does a pretty decent job concerning the straightforward maths problems, I personally found their word problems a bit too easy as compared to the real test. You might want to check zuleron's 700+ quant questions from the GMATprep software for some extra practice, but only if you've already taken both tests. You don't want to "spoil" your score!

There's one thing to keep in mind though: since you're already at a comfortable level with quant, don't forget about verbal. I assume (from your name) that English is not your first language. If indeed you have some trouble with it, then I suggest you invest most of your time in verbal and just work a little bit on quant. If you are by any chance Indian, please remember that Indian test-takers usually get great scores in quant but struggle with verbal (that's probably valid for most non-natives, but most of the time I notice it for Indian forum members). Even if you get a 50 in quant, if you only get a 20-something in verbal, that's going to hurt your score a whole lot!

All the best and I hope everything goes smoothly with your prep!

thanks a lot DANA.....that was the reply i was looking for
yep you guessed it right, i am in fact an INDIAN. and i am doing exactly what you said about verbal, i just started preparing and am actually starting to feel comfortable with CR.
would start working on SC soon