Wow! This is quite a mall. Visited on Family Day 2017. I'm not sure I've ever been in a busier mall. Of course many of the area malls were closed for the holiday, so no doubt that increased the crowd even more.
I've been to malls with more top-end stores in the US but haven't been to one yet that impressed me more with sheer size. With a labyrinth of a mall like Eaton Centre and an adjoining Saks Fifth Avenue you are bound to find all you need here, and plenty of top-flight stores to boot.
This mall is HUGE! Maybe the biggest mall I've ever been in if you count all the nooks and crannies you can walk to without ever stepping foot outside. While we walked from parking at City Hall, the fact that the subway system is connected directly to the mall was great and novel to me.
Other people have given you all the logistics and finer details of the mall - I just wanted to add my two cents - color me impressed! Definitely worth a visit when you're in Toronto.