The AGO is the best art gallery in town, despite a lot of problems over the last few years. They've been half-open during a long-running and much-touted Frank Gehry renovation, but still charged exorbitant admission rates for some lame exhibitions.
Yet they've still snagged some impressive international shows, so there's usually been something prestigious at the AGO at any given time. (The excellent Turner-Whistler-Monet show was here before it went to the Tate in London, for example.) They've been totally closed the last few months, leading up to the big re-opening in November.
The collection is pretty good (though not up to the standards of the best art museums, unfortunately). Apparently much more of the permanent collection will be on display after the reopening, since there will be more gallery space. Check back for an update in a few months.
I can truthfully say I've had my art displayed at the AGO. I went to their art school for kids back in the day, and they used to put up the best student work along the basement. A couple of years later, one of my drawings was still there! But now it's long gone; gotta make room for the younger generation, I suppose.