I've never had a major problem with any shipping company.
For sending to the US, I use Canada Post which = USPS, and everything seems to work fine. Sending within Canada = we use DHL at work, and things often show up early and in perfect condition ... I personally use Canada Post.
Receiving from the US ... I prefer UPS or USPS. UPS is great if you don't have to pay brokerage fees ... USPS is great if you do have to pay, but slow as shit across the border.