We did see humpback whales. No, they didn't jump out of the sea and perform tricks in the air. They don't actually breach that often, so don't be mislead by the pictures you see in ads.
Beware of a crazy guy equipped with a microphone. All was well when he read out information on humpback whales, their habits and behavior. But when he ran out of text he slipped into the stand-up comedy genre, of a very cheesy sort, and kept blathering pretty much until the boat docked at the pier again. It was a torture. If you're not into that kind of entertainment, bring ear plugs.
The tour is very weather dependent. I had to rebook for another day because the first trip I booked was cancelled.