I live in Pittsburgh, (3.14 hours from CP) and have purchased season passes for the past 3 years. It's definitly worth it if you plan on making more than 3 visits to the park. Additionally, if you plan on visiting any other of Cedar Fair's parks (being in Chicago, you are relatively close to Valleyfair, and World's/Ocean's of Fun) the season pass would work for those parks too!
Take time to plan out your trips to the different parks, do a cost analysis, and you may find that a season pass would be worth while.
P.S., please be more descriptive in you topic title... thanks!
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Neil
By popular vote, the official start
of the Millennium has been moved to
May 13, 2000