Looks to be a solid addition, 13 acres, 25 slides, massive wave pool, budget approx. 35 million.

http://www.sixflags.com/parks/hurricaneharborchicago/mediacenter.html

and a great image of what the park will look like..

http://www.sixflags.com/parks/hurricaneharborchicago/images/Birdseye.jpg

A separate gate admission, all for less than Winnie The Pooh... :D