Anytime I can clear customs and immigration before my flight is a huge plus with me. Last thin I want to do after flying for hours is to deal with customs and immigration.
At the Toronto Airport the line moved very fast and expeditiously and the agents I had to deal with were polite which is also a huge plus as some of them just seem miserable.
My two areas of improvement would be:
I have global entry. I should not have to wait in an additional line after doing the kiosk. This is not common in other airports.
The global entry kiosk is not meant for people above 6 feet. When you are taking the picture give warning so I can duck. Otherwise you just get my shirt and chin which has happened twice now.