I lived in Toronto for over 25 years before I ventured off here (and only because the ticket was free). I definitely would not pay to see this place, it is totally not worth it.
The castle is really big. I came here on a hot summer day and found myself sitting in the courtyard for over 2 hours because I couldn't find any motivation to walk the giant palace. I ate some gelato ($4 a scoop). It was very bland, wouldn't recommend.
I didn't really look at all the rooms in depth but spent about 30 minutes walking around the castle in the end. The basement where they keep the stables is impressive. I also had fun climbing the tower, although the view is not that impressive.