Well, doing official questions is never bad for you. If somebody buys you the paper tests as a gift, thank them, and do all of the questions. They can't hurt.
On the other hand, the paper tests are from the early-to-mid 1990s, so you're looking at some pretty old questions here. They're still useful, since the main quant and verbal question types haven't changed all that much since the 1990s, but these questions aren't necessarily as fresh as, say, the GMATPrep Question Pack.
Each paper test contains roughly 110 questions, and just over half of those questions are verbal. Since the paper tests aren't adaptive, the questions give you a broad range of difficulty levels; if you're a relatively advanced GMAT student, plenty of the questions will seem painfully easy to you, especially on the quant side. A relatively small proportion of the questions are tougher, so if you're already in the 650+ range, you'll be challenged by a minority of the questions.
The biggest issue is that plenty of the GMAT Paper Test questions appear in other resources (various editions of the GMAT Official Guide
, the official GMAT quant/verbal supplements, GMAT Focus, the GMATPrep tests
, and the old PowerPrep tests). How many questions overlap, exactly? I'm not certain, since a lot of the questions appeared in really old OG editions or the obsolete PowerPrep tests, and my memory of those is getting foggy as time goes by. But my guesstimate is that 40-50% of the questions appear in another resource. You won't recognize nearly that many, though--unless, of course, you're a connoisseur of obsolete OGs and practice tests. The overlap with the newest editions of the GMATPrep, OG, and quant/verbal supplements is probably in the 15-25% range if I had to guess.
So are they worth it? I guess it depends on the size of your wallet and the size of your appetite for new questions. A set of three tests costs $29.99 on GMAC's website, so you're paying about $10 per test. That's not insanely expensive, but it's not necessarily cheap, considering that relatively few of the questions are both A) challenging, and B) don't appear elsewhere.
If you have the money and the time to do them, go for it. But they're not a great substitute for the Official Guide or the quant/verbal supplements or the GMATPrep Question Pack.
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