Having the explorer pass made sightseeing very easy and cost effective. I loved having the ability to choose which sites I wanted to go to (and how many). I'd highly recommend it!
The hop on hop off bus experience was not what I expected. I had hoped for a lot of information on Chicago. We did get some but l had hoped for more too much trying to be stand up comedians. I loved our time on Navy Pier. The Architectural River tour was marvelous. Our guide was outstanding - very knowledgeable and fluent. It would be helpful if the guide was more specific about what is covered and how to access things. Remember you are dealing with folks who are not familiar with the city.
Highly recommend, excellent way to see the city and do the activities. There are many great museums and tall towers. City is small enough the getting around would not be a problem. I think we walked 3/4 of the city one day. Chicago Explorer Pass definitely helps. I would recommend hop-on hop-off bus to get idea of the city and do boat cruise around the city.