As someone who hails from Ottawa, where Shopify is headquartered, this is wonderful news. From my perspective, they have contributed more to the tech and startup community in Ottawa than anyone since Nortel. Kudos to them on their success!
Except now instead of focusing on the other aspects of your business you need to focus on the infrastructure as well. What if your products get super popular? Not you'll need to work on scaling out your store which will cost a boatload in equipment and specialization.