This is one of Toronto's best attractions. The Michael Lee Chin's crystal was a somewhat controversial addition to the museum, but I think it turned out bold, unique and beautiful.
The museum is big with lots to see - lots more than can be seen in one day. We got the family membership which works to be quit reasonable. The kids can't get enough of this place. The exhibits they are most excited about are the dinosaurs, and the bat cave.
Make sure you catch the Earth Rangers show when it is on (occurs several times a year.) We have seen the show several times, and it's been exciting every time. They exhibit some large felines, and some magnificent birds which swoop right over your head as they fly across the auditorium. It is fantastic.