We found this to be a great tour.
On the plus side, this is one of the few trips that gives you about 6.5 hours of free time at Key West. We did the glass bottom boat and then walked around town and visited the beach. We had plenty of time for this. The driver was friendly and explained things quite well beforehand.
On the downside, there were no toilet stops on the way back - a good 3.5 hours from Key West to Miami. This became quite difficult with the kids. On the way out, there is a stop at a Macdonalds.
Other notes - You can choose to buy the optional activities on the bus. There is time for only 1 optional activity, so you need to choose. The glass bottom boat is ok - coral is not great. It was quite hot on the boat. However, on the way back, we saw dolphins. If we had our time over, we'd choose parasailing instead.