Excellent!! New 'Tilt' feature had just opened on the day we went so that was an added bonus (extra $5.00)
Best view of Chicago, much better than Skydeck. One has to perform some tricks to reduce the blinking in glasses while taking photos. I would highly recommend the "Sun and Stars" option as Chicago looks great both in the day and in the night.
I went at night unfortunately. The views are still good but if you are a stranger in town it is difficult at night to pick out the buildings that he audio guide is telling you to look at. If I had more time in town I would have chosen the daytime instead.