FedEx into Canada is horrible, the rates seem relatively reasonable until a month later you get a bill in the mail for outrageous amounts in "brokerage fees" that are typically only $5 when coming in via USPS/Canada Post. As an example, my wife bought me one of the iPure docks for Christmas, a $100 purchase with around $10 shipping, a few weeks after it arrived we get a bill for almost $50 most of which was brokerage fees. If that had been USPS it would have been $10 ($5 brokerage, $5 GST), paid up front at the post office.
On another note, if I get something shipped via FedEx or USPS and I'm not home to get it I then have to arrange to go out to their depot both of which are out by the airport and FedEx only has a window of about an hour a day that you can pick up, alternatively, I can pick up Canada Post packages at my local postal outlet anytime between 8 and 8 Mon. - Sat.
I've been shipping via USPS/Canada Post for almost 10 years now, occasionally packages take longer than expected but generally I've been very pleased with the service. I'll typically avoid buying from a company if they won't ship via USPS/Canada Post, it's just not worth the cost and hassle in dealing with them.