Air Canada isn't the best I've experience, but it's not the worst either. They are middle of the road for me. I fly AC most often in Canada because the other option isn't an option if I need to be somewhere at a specific time or day.
I'm not a regular business traveler, but I do fly regularly. Mostly for pleasure, but some business in there also. Most of my flights have been on time. The staff is courteous most of the time, but maybe because they know I fly regularly.
The biggest inconvenience that I've experienced is flying out of Toronto. When I arrived at the check in counter, my flight was delayed for three hours. I asked why I wasn't called or notified (by phone, email or text - I was subscribed for it). They couldn't explain. I then asked if I could have a meal voucher because of the delay and that I needed to eat dinner and that if I were notified, I could have had dinner before I arrived at the airport. She thought about what I said for a moment and then told me it wasn't company policy. I requested to speak to her supervisor. After summonsing the supervisor, I did get a meal voucher in the end - but not without a hassle. Where it should have been done without asking. Really, is giving me $10 for a meal going to hurt them considering I spend thousands of dollars every year with them?
The other option in Canada is worse, so AC will have to be it for now. But I wish there were something better.