Excluding the exchange rate, Canada has a HUGE tax that apparently you can get back if you leave the country. I have NO idea how to get it back and the H boutique had no idea either. When I asked, they said there is no such thing. A tpf member told me about being able to get the tax back, but hey, lets be honest, I just cannot be bothered!! I still got the bags at the extra 12%, but still, it does not end up being the same. Also, the Canadian dollar is quite strong these days, at only about 1.12 CAD per USD, so very little impact. Try to use your bank issued Visa card, they will ALWAYS have a better rate than AMEX. AMEX is known to be easily a few big figures off on the rates. If you do purchase there, I always take the bag with me and have them ditch the box or ship it to me. The boxes have been lost, delayed, damaged...but thankfully I had my bags in tow vs. shipping. For some reason shipping from Canada has more delays and problems than overseas.
Unless there is something you see that is out of this world gorgeous (which happens a lot in Canada!!), it's cheaper to buy your bag in the US.