I read over the reviews before going, so was well advised about getting tickets in advance. I was braced for crowds.
To my surprise, we walked right in. Even the "line" for tickets was only two or three deep. Other than one poorly designed area (with information and a model of a shark) it was not overly crowded.
For sure it has the Ripley's Cheese factor but also very good displays. I wonder if some of the crowding mentioned was due to the place being very new.
If you enjoy aquariums (aquaria?) by all means, go. Get tickets in advance and go on a weekday evening as we did. Family friendly. Expensive - but when you consider the overhead of managing so many different aquasystems and the price of Toronto real estate, understandable.