Big fan of GMAT Hacks here. I've been reading Sackmann's material and have some of his question sets. Not all 1800 questions, though. Sackmann is a believer in quality over quantity, and I agree with him. I really have no use for 1800 questions. I'd probably never even look at half of them.

Yes, there is some great material there, however there are some typos and incorrect answers. Again, quality study is more important that quantity.

Can't really fault a guy for typos, can you? Along with them comes errata or newer revisions. And I have yet to see incorrect answers in his recent publications, so am curious as to exactly what you are referring.

Overall his stuff seems very well vetted, and he's been around for quite some time now. His questions are very well designed and model actual OG or GMATPrep type questions. I'm personally not a big believer in the theory that overly complex or computationally intensive practice questions make for good study aids. So overall, I think Jeff does an excellent job. And I have zero, and I mean ZERO, affiliation with him.

Curious about your signature info, by the way, Jim. You say the best source for GMAT math problems you've found is at gmatprepbook.com. Interesting. There is zero info about these problems or any of their product offerings at that website. The website has only been registered since mid November of last year, according to internic. Two months of existence. So how'd you happen to come across this product from such a brand new website with no information posted whatsoever? Or are you affiliated with that website? And is it just a coincidence that you registered your beatthegmat account in mid November as well? Just curious. Thanks.