Buying the CityPass in advance turned out to be the only way to go. Getting to skip lines, especially buypassing 100+ people in line for the Willis Tower, was priceless! There was so much included with this pass, that we almost didn't get to do all the activities. I definitely recommend buying this pass!
If you have four or more days to spend in Chicago, or if you start out every morning very early and afternoon until 6 pm, the City Pass is a great deal. Unfortunately, we only had three full days and being over 65 years of age, we don't have boundless energy, so we didn't get full use of the pass. Where we did use the pass, it permitted us to bypass long lines (and they were long especially on Saturday and Sunday) and to see exhibits that you would not see if you bought the basic ticket. Even though we didn't use two of our five passes, I feel that we easily got our money's worth in terms of admission fees. The convenience of bypassing long lines is certainly a bonus.The passes are good for nine days, and I'd say you need to sightsee 3 or more days to get the most out of your City Pass. After all, you don't want to ignore some of the free attractions, like the Chicago Cultural Center, the Bean and Buckingham Fountain, to mention just a few.
Brilliant offer to see some of the major - and therefore busy - spots in town. We bypassed a ninety minute wait at the Skydeck which straight away made it worthwhile. Plan your day around the other offers; the science museum in Hyde Park is definitely worth the trip out to Obama territory. I'd skip the Planetarium and use the ticket for the Art Museum which, contrary to advice in our guide book, is not free on Thursday evenings. So, good to structure your visit and beat the crowds.