Can I ask you guys which fingers you are using to navigate? I keep seeing reviews or people commenting that their hands hurt when adjusting to using the trackpad, and I never had that when I went back to using Macs.
Then I realized when I scroll through OS X, I use my middle and ring fingers instead of my index and middle finger. Using the latter feels uncomfortable and almost unnatural. If you're using your index and middle fingers, I recommend trying your middle and ring fingers instead and see how it feels.
I have been using my middle and ring finger to scroll and find this more comfortable than the Magic Mouse. With the mouse, I always felt like my hand was stuck/cramped in this cupping shape to hover over the mouse.