So this is actually in Mississauga, but services Toronto. There's a streetcar option to the Kipling line (I think?) that allows you to take the TTC downtown.
I've never actually taken public transit from here, but I've heard it's easy. There's multiple lounges and Nexus lanes. They also give security priority to Nexus holders so that's a plus.
The food options, at least in terminal 3, are terrible. Bland and boring all the way. The duty free alcohol is actually more expensive than just buying it in the US. Even in Chicago where sales tax is 9.5%.