As a Mississaugan, I have to dispute that traffic in the GTA is not bad.
1. I was driving home from a friend's in CityPlace a few weeks ago (Spadina & Bremner) at 12/1 am and Spadina was jammed, Lake Shore was jammed, because the Gardiner was inexplicably closed. So I took Lake Shore for a bit, before I saw others doing U-turns, so I copied them, turned onto Yonge, drove up to Eglinton, then took the Allen to the 401 and got home that way.
2. Another time, going home from CityPlace again, again around the same time, and this time the Gardiner was fine, but the 401 after the 410/403 interchange was a nightmare, with the two right lanes closed I believe. It was for additional Hurontario bridge demolition I believe. Didn't go anywhere fast on the 401 at that time either.
3. Last night I drove myself and a couple friends downtown to see Harry Potter at Scotiabank. Left Square One around 9:30 pm. Traffic on the Gardiner was a nightmare. Turn on the radio: Gardiner was closed between the Humber and Jameson. I hadn't even thought to check what the traffic was on a Thursday evening. By the time we arrived downtown around 10:something, we noticed the downtown core was overrun with cars. It appeared to have been caused by Blue Jays fans. It drove me mad.
On the whole, I find traffic in off-peak times to be worse that peak times. (e.g. my drive to work at 6:30/7:00 401/410 is pretty quick around 15 min; back home by Tomken/Derry/Mavis is more like 30 minutes; but in either case traffic at least moves at a decent clip, aside from the 410 south/401 east on my way home if I make the unfortunate choice to "try" them out again).