Not very big, but the I really dig the concept of having a sculpture garden. Good for you Toronto!
As mentioned, they switch things up every now and then. I don't usually make a point to go check on the garden, but when the weather is good and I'm in that neck of the woods I'll pop in and poke around. Seems like a nice place to set up shop with a book as well. In the past they've done pretty neat stuff here for Nuit Blanche as well.
Overall, if you're not from town and nearby definitely check it out. Unless it's winter/tundra time, probably best to seek out indoor art!