SHOP (Shopify) is doing pretty well and their upcoming plans/platform seem to bode well for them.
My company, Pavlok (http://pavlok.com), is built on Shopify, and it's helped us hook up all our shipping/billing/marketing/payment services. Shopify is also a really awesome company -- we were one of their 2015 winners of their Build a Business Competition where they flew us to Necker Island to spend a week with Richard Branson, Tim Ferriss, Seth Godin, Daymond John, etc. Not many companies make a trip like this happen :) https://youtu.be/tmuF1xaW3Z0