Just a word of caution about traffic jams on the QEW westbound on weekday afternoons and early evenings.
I've been to Buffalo a few times to see the Leafs and Sabres play and it has always taken me 2h 30 m or more to make it to the Canadian side of the bridge (Lewiston or Rainbow are my favourites) from the west end of Toronto. Granted, most of the games I have been to have been on Friday nights but I'm not sure it is much better on Mon-Thurs.
It can be slow all the way from downtown TO to Burlington. It usually picks up at the Burlington Skyway, but don't expect to be doing 120 (not that you would, as it is - of course - over the speed limit...). Speaking of that, my best time was very early one summer Saturday morning: High Park to the US border crossing on the Lewiston Bridge in 62 minutes. Not too many people on the road that morning.