I had the reverse experience... the second part of the test I tried was easier than the first part... so much so that it was scary. The first half, it felt like it was taking forever for me to hit the keys, like I was in a slow-motion nightmare. The second part was like going down a greased slide.

Good catch. There is a small order effect on these tests. From the Project Implicit FAQ:

Q: Could the result be a function of the order in which I did the two parts? I had to group one category together with pleasant words first. I then found it difficult when I later had to group the other category with pleasant words.

A: Answer: The order in which tests are administered does make a difference to the overall result in some tests. However, the difference is small and recent changes to the test have sharply reduced the influence of order. Because of this order effect, the orders used for IATs presented on this website are assigned at random. For any data we present, we are careful to be sure that half the test-takers got the A then B order and the other half got the B then A order. With the revised task design, the order has only a minimal influence on task performance. If you want to check whether the order made a difference for you, you can take the test again and complete it if you get assigned to the reverse order. If you do take the test twice in different orders and get different outcomes, the best estimate of your result is intermediate between the two. For more information about the order effect, see this paper