"Im under the impression that in order to achieve a high score, you need to do well on the first part of the test, so the computer can determine a low-ball score. Then in the second part, depending on how well you did, you'll receive harder questions."
I did not notice any huge difference from part one to part two on the verbal. Yes, the test adapts to you, but the change in the question pool is not so noticeable that is distracts you. In fact, worrying about "huh, this question is hard. I must be doing well!" is actually pretty counter-productive. Trying to gauge the difficulty of your questions is just a waste of your time.
As for "harder" tests, I agree completely that some tests are harder than others. I did significantly better my second time on the verbal. Why? I don't know; I retook to boost my quant score! I just got easier questions the second time. But when people talk about that, they're just talking about the luck of the question pool, and not some formula out there to receive the hardest questions to get the best score.