IMO, first questions do count more.
Firstly, from my observations, there is no "hit value" of a question, but a "miss penalty" - that is, the easier the question you screw up, the more points are deducted. First questions in a section are relatively easy, therefore you better do them right.
And secondly, they affect the complexity (and value) of the questions that follow. When I was doing GMATprep, I had 5 misses in a row at section end and still got a 770 - because my first 15 answers were correct, and I reached the "hardcore" zone. There, faults were not penalized so hard, cause the questions are considered very tough.
(Disclaimer: I have no proven data about GMAT scoring schemes, these are mere guesses based on my observations.)