I visited Toronto in late Jan 2012. I was dissapointed to realize that the show "Diners Drive-ins, and Dives" had no Canadian restaurants. I did a search for Canadian DDD's, and found this posting on Chowhound:
http://chowhound.chow.com/topics/619901
where Burger Shack was mentioned.
I went one night during the trip; I got the bacon cheeseburger and fries. My American debit card wouldn't work in the ATM they have here, but thankfully they took US Dollars (at face value).
The burger was good, but it tasted like spiced lamb, not beef. It was a very interesting an pleasing taste. The fries were very good.
No complaints, and I wish I lived closer so I could try more items.
Basically a step below a diner, but they do things very well.