I'm not a waterfront resident so this is already not in my backyard. I am a Torontonian who uses the waterfront as much as I can. The "whisper jets" argument is so dishonest and based on a technicality that most people (looking at you) don't check. Yes, the newer jets are fairly quiet in flight and even on approach but all jets, particularly on a short runway, need to use thrust reversal to slow the plane down. Those are — pardon my French — f*cking loud! Even the existing prop aircraft rev their engines prior to takeoff and I hear them performing maintenance at night when I'm in the office late. "Just as quiet as the turboprops" isn't the argument you think it is because those aren't quiet either. Expanding the airport for jets would mean far more of takeoffs and landings.
The thing is, a downtown airport isn't even a good proposition anymore. UP Express has deflated the need for one. Yes, it used to be nice to avoid Gardiner traffic or a long round about way by subway and bus shuttle but today I can get to Pearson from my office on Bay Street door to door faster on UP Express than to Bathurst Quay in a cab or a shuttle in traffic. I don't even have to go outside if I take the PATH on a snowy cold winter day.