This is an idea that will probably never fully go away, but GMAC itself has debunked the "first 10 count more" myth, and says explicitly that all questions are worth the same amount. (We touched on this in a blog post last year:
https://blog.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/10/tho ... ummit.html)
Basically, it boils down to the fact that the test needs to be flexible enough to account for false positives and false negatives -- the chance that some people will guess right on a question when their true ability level suggests they'll get it wrong, or they really know how to do a problem but slip and get it wrong. If the test were too rigid, getting the first few questions right might permanently put you in the "700+" camp, even if your true ability level is more like 600. But, the test is actually much more flexible than that: Even if you get the first ten right, if you start start missing questions that are appropriate to a certain level, it will start to knock your score down. Run out of time toward the end of the test, and this is even more likely to happen, and your score can drop dramatically. So, even if you "test above your level" early in the test by taking extra time to carefully work through every problem, you won't be able to keep up that charade forever, and the test will definitely "find you out" sooner or later.
Think about it this way: You can't go back and change answers later, and it's worthless to have 4-5 minutes left at the end... All you can use that time for is to do a really good job on the last question. So, spend the extra 5-10 seconds on the first few problems to make sure that you're not making silly mistakes, and to build confidence (and, like that Doberman guy says, build a rhythm). But don't plan to spend an extra 25-50% on the first 10 like some people recommend... That's just poor pacing!
Scott