We used the Explorer Pass for 3 activities- the Big Bus Tour, Willis Tower and the Architecture River Cruise. All 3 were top notch attractions. The only negative that I can mention is that the Willis Tower entry said skip the line, but it didn't really skip anything, although since it was not crowded it didn't really make much difference to us, but if you wanted to use it to skip a long line it apparently would not have done what you were expecting.
Good value for the options we chose. Liked the ability to use the fast pass line - this saved time. There were some items that were not included with the pass that were not clearly indicated on the terms and conditions. 3D movie at Field Museum not included and only 1 special exhibit.
The tour on the Mississippi was just amazing. The buffet was great, nice friendly staff and the view was also great. We just loved this tour, was the best evening of our whole vacation. The only thing I felt was a pitty was that they lost our picture that was made in the beginning, I would have bought it if they didn't.