As a Canadian living in the US, I've had a lot of trouble with US Customs at both airports (YVR, YYZ) and border crossing (Vancouver, Niagara).
However, I don't deny that it is at times necessary for Customs officers to be more strict. I would rather the officers do their jobs correctly and prevent incidents (drug smuggling, terrorism etc.) from happening.
Although at times they do seem to be unnecessarily aggressive.