Having lived and commuted by car and bike in downtown Toronto for 25 years, I can say that, for the most part, downtown drivers are generally aware and considerate of cyclists. There's so many of us, particularly from May-October, they have no choice. They're not perfect and the conditions aren't perfect, but they're not bad either. I've never encountered guns or crack-heads, as Steeker remarked, nor would I agree with Swifferman that you should avoid downtown Toronto: it is far better than North York, Etobicoke and Scarborough for cycling (imo). You need to be experienced somewhat to drive on the major routes downtown, but there are plenty of secondary routes that are less-congested and less dangerous (Harbord, Davenport, Sherbourne, etc) and may have nike lanes to make things easier. A different attitude seems to exist beyond the downtown borders, however.

And, as for motorists: I've driven through many American states and will state unequivocably that highway drivers there are far superior to highway drivers here. I don't know why, but they are, and it was a pleasure to drive through Ohio, New York State, Pennsylvannia, Virginia, Michigan, Illinois, etc compared to the 401.