We hadn't gone to the Ontario Science Centre for quite a few years (maybe 7 or 8 years), but after a mini-trip to Ottawa, and then a trip to Niagara Falls, were called off due to inclement weather (the former because it was too warm, and the latter because it was too cold), we decided to just bring the kids to the Ontario Science Centre today.
The place has improved dramatically.

7 years ago the OSC was largely full of malfunctioning equipment - leftovers from the original installation - and a lot of rather terrible computer demonstrations powered by Apple Mac Classics (though of course they weren't called Classics when they first made them, but they still were eye-opening to a lot of visitors years back, when the idea of a mouse controlled GUI was pretty novel).
A few of the better old displays still exist, include some Mac Classics still going strong, but they are now supported by a lot of fabulous new displays that kept our 3 year old overloaded with excitement until closing time. She is on the young end for a visit to the OSC (although the KidSpark area was perfect for her), but even much older children were having a blast. Parents were learning something as well, and indeed parents were often the first to start pressing the buttons or pulling the levers on the interactive displays.
All in all it really has improved, and was a very enjoyable visit. It's great to see such an attraction getting a facelift (much of it is ongoing, with several huge new improvements being built right now).
Now if Toronto could get a real world-class Aquarium.