Sorry to hear about that as well...
When I was hearing the planes last night (from Reagan), I was wondering which planes were landing, but it turns out that flights were LEAVING Reagan well past midnight (unheard of, usually)...then checking on United.com, I saw the crazy cancellations and delays going up and back to at least Chicago, so i'm guessing a bunch of flights were messed up around the board.
At least you made it up there last night, and although 5 hours in any airport isn't much fun, I'm curious what you ended up doing at YYZ. I'll be there shortly for quite a long time, and i've never spent much time in the airport before, so i'm just curious what you occupied your time with, unless it was sleeping, which is definitely understandable!
-jeremy