I've never had a nice experience returning to Canada (either by plane or car) after a trip to the US or Mexico. I get the full "random search" in a secluded room every single time.
After a bit of A/B testing, it seems to have been "older woman traveling alone with a fancy watch" that was flagging her. Without the watch, the problems went away.
Going back to the US (even as a non-citizen!) I usually just got a "Welcome home!".