Well, it is one of the few real tourist attractions in Toronto, so it tends to be crowded and more than half the time is spent just navigating the lobby waiting in lines and getting the the elevator.
Otherwise, it is supposedly higher than Space Needle in Seattle or Empire state building, but that high up - you actually can't really tell the difference. They all look the same.
Might be a nice place to visit with a group or to take someone there if you live in Toronto, but it is on the pricey side.
Try to go around the time for sunset. That'll probably get you the best views.