It's really unlikely that you'll have a similar experience. Pretty much everyone I've talked to went through with no problems. But here's the story:
I came up in November of last year. We waited until my husband had been approved for sponsorship so that we could have that "proof" of the application in process. When I got to the customs agent, they asked me, "How long do you intend to visit Canada". I basically couldn't give them a good answer. I said that I was intending to stay until my PR application was processed and planned on extending my visit if needed. I couldn't give them a definitive timeline, and of course, they did NOT like that. I was told to go around the corner and talk to an immigration agent. This guy was...something. He started off very rude and condescending. I told him what I'd told the customs agent. I said that I'd stay the full 6 months that I was allowed to be in Canada. He says, no exaggeration, "As long as you're ALLOWED to be here?! What does THAT mean??" Admittedly, I'm nervous at this point. I said, "American citizens have can be in Canada for up to 6 months....so I'll stay for that length of time and extend the visitation if I need to." He says, "Excuse me? You don't have the right to be here at all. I decide how long you have the right to be here! And what are you going to do after 6 months??" I'm nearly in tears at this point. I said, "Extend my visitation...?" He starts laughing and turns to the other immigration agent, "Visitation? What is that? Isn't that something you do at a funeral?" (seriously, I'm NOT making this up). He finally gets serious, and just starts hammering me with questions: How old are you? Where were you born? Where does your husband work? How much does he make? How tall are you? What is your eye color? What's your husband's address in Canada?
He asked a few of the questions more than once and he was firing them off very fast. It was obvious he was trying to catch me in a lie and trip me up. Then, the instant he decided I was telling the truth about everything, his entire attitude changed. He was suddenly friendly, patient, answered a few questions for me, and we joked around about unreliable computer systems. He issued me the visitor record for 1 year, reminded me that I couldn't work, but was very encouraging that the process shouldn't take too long.
I still shake a bit thinking of it because I was REALLY convinced for a minute or two that I'd have to get right back on a plane and go back home (with my two large dogs sitting across the airport in freight cargo). Even my immigration lawyer was shocked when he heard what went down. And trust me, I have zero problem with authority. I was nervous, but was never disrespectful or demanding.
I really do think this was a "worst case" story, and extremely unlikely to be your experience.