I tried this strategy on my first try of the GMAT (Dec 2007).
It did NOT work for me (low 600s). I ended up running out of time and missing some easy questions on the end of the quant section.
I tried the average of 2 mins/question on take 2 (June 2009), and did much better (broke 700).
It does appear that getting early questions right will get you to harder questions sooner, but if you crash and burn at the end on questions that are rated lower than 700-800 difficulty, your score will crash and burn. That much I can assure (from personal experience).
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