The ass chewing by border guards is dependant on which guard you get and how bad he/she hates his life that day...
I live right on the border and absolutely detest crossing. Got sent in to secondary on the US side on our way to a country concert for over an hour.. Missed half the concert and the one guard was circling like a shark eye balling us and at one point tried to instigate a confrontation with us.
On the other hand, a Canadian officer politely told my brother in law he had to return the coral he had to the store in Buffalo and allowed him to do so.
I've had a handful of negative experiences by a handful of angry customs people, and have witnessed some pretty stupid behaviour directed at other people that has made me keep my butt on this side of the border as much as possible!