I went on one of their one hour harborfront cruises and enjoyed it. For a total Toronto n00b like me, it was great to see the gorgeous views on a sunny day and learn a few fun facts about my new city. The tour guides are young and kinda corny, but not uncomfortably so. However, the best part was the stop on the Toronto Islands. They give you the opportunity to get off the boat and spend time in the park before taking a later boat back. Be sure to take one of the earlier tours so you can spend as much time as possible strolling around the gorgeous park!
Shutterbugs take note: the tour offers great views of the Toronto skyline, so schedule your cruise at a time when you can take advantage of good lighting! :) The evening return cruises off the island can get a little crowded, but if you can snag a good seat it's totally worth it.