Further to my earlier post, the Canadian dollar was worth more than the US dollar last night for the first time in 31 years. As I write, $1CDN will buy $1.0014USD!
As this Bloomberg story notes, the Canadian dollar has appreciated by more than 62% since 2002. This has also largely been a real (as opposed to nominal) exchange rate change, as the inflation experiences of the US and Canada have been similar over this period.
There's a warning implicit in the there for all international transactions: exchange rate fluctuations are huge, and can easily dwarf all other risks faced by businesses.