Verbal questions are pretty much mixed up although there are not many hard questions in the beginning of the individual verbal sections. As for quant, there is definitely an increasing difficulty trend in DS and PS sections. The last 100 PS and 60 DS questions are definitely much tougher than the early ones. If you are short on time, gauge your skill level and if you are innately good in math, only do the last 100PS and 60DS questions. Of course, I was talking about the 10th edition. I do not know for the previous ones.