I suspect this has to do with the fact that you are Canadian. I am American, I have always found crossing back into America to be much less of a hassle. The Canadians have been stone-cold S.O.B's whereas the Americans are just rude.
Ironically - I have precisely the opposite experience. As a Canadian on a TN-1 Visa, approximately 85-95% of the time (more often in the last few years) - I get fingerprinted and asked a single question "What are you doing" when I answer back "Going to work in Redwood City" - the interview is terminated and I'm waved on.
Coming back INTO Canada though, and I'm subjected to the third degree - asked why I'm coming back, where I'll be going, what I'll be doing, etc...
But, after having done this six times a year for 13+ years, it's become pretty routine so at least I know what to expect.
At grave risk of redundancy: I have had the opposite experience. Canadian customs have always been friendly to me, and US customs at the Canadian border have always been total dicks.
I used to work and live on opposite sides of the US-Canada border (for around 1.25 years -- I was too lazy to apply for the pre-screening to get to the front of the line... plus when it gets backed up on those bridges you still have to get through the lines of cars just to get to the pre-screened booth). So I have a lot of experience with Border Patrol (at least on the Rainbow Bridge -- I avoided the other ones since I figured they would be nicer at the one most tourists would use).
Canadian Border Patrol:
* Very professional
* Demeanor ranges from 'stone cold' to 'polite and pleasant' (in some cases 'warm' too)
* Once had an asshole of a Canadian Border Patrol guy that said my story was 'confusing' and that 'it takes a lot' to confuse him. (In a total, "I'm talking down at you because I'm a law enforcement officer that needs always project authority" sort of way)
* I once was in front of some people that got turned back from the Canadian border (one of them wasn't a US citizen and was trying to use a Driver's License as ID to cross the border) and at no point did I feel that the border people were acting like assholes to the couple trying to cross.
US Border Patrol:
* "military police with a chip on their shoulder"
* One time I had a border patrol guy get pissed at me because he accidentally set off the car alarm (he asked me to hand him my key fob, and he pressed the f-cking red button on it).
* One time I had a US Border Patrol officer try to crack a joke with me about a recent local suicide (it happened at the casino I worked at). It was in total bad taste... and I'm someone that finds humor in crap on 4chan /b/. I just kinda nodded to get through the border (and because the casino didn't want us talking about it at all either).
* One time I was almost pulled out of my car because they confused "I work at the casino" with "I won at the casino." The guy asked me how much money I had on me, and got pissed off when I told him, "I dunno, maybe $5 in change." (The odd thing about this was that he and his 'partner' were wandering around through the mess of cars backed up over the bridge going into Canada . They were US Border Patrol Officers, why are they patrolling the people going into Canada?)
Overall, I've only ever had my car searched 2 or 3 times (all by US Border Patrol as a US citizen). (One of those times I kinda agreed with the search even though they told me it was a 'random' search. I had gone across the border to deliver a present because it would be faster than shipping it. When asked how long my stay in Canada was I replied, "about 20 minutes." The reply I got was, "You've been randomly selected for a search. Pull around to the spot over there and take this slip with you."... At least they could be honest and say that I was suspicious...)
