Low dollars improve our competitiveness and the attractiveness of our exports.
Not to mention, foreign investment can increase because their currency now goes farther here (lowering their costs).
It's also good for our companies which operate elsewhere, as they get their earnings converted for more Canuck bucks.
For domestic consumers, it does make imports more expensive, so there is some give and take - but to say that a low dollar is bad for the economy is false.

Your claim that a high dollar pays off debt faster is ONLY true if we are paying foreign creditors.
Local debt (like the kind most Canadian citizens deal with) is in Canadian dollars - so no change.