Right now, when you twist your hands around they bunch up at the wrist, and it looks kind of ugly. If you look at your arm in real life, you'll notice that when your hand rotates on that axis, it's actually your arm that's moving. Specifically, the two bones in your forearm are twisting around each other. I'm not sure if this would be a simple fix with the current IK arms or not, but I think it would look a lot nicer. (Especially with the Wristbands!)