I think that all of the powers are neat, and I don't really think that they'll have any significant effect on the balance of the game.
However, I do have one question. Why do Scrappers only get three pools, while Blasters, Defenders, and Tankers get 4? Controllers get 5 too, and it's all nice. But why do Scrappers get a smaller number of choices? I'm not griping, mind you, just legitimately curious. ^__^