The ability to create custom products with multiple variations of sizes/colors etc without having to go through an outside vendor like Magento or Bigcommerce was great! I wish there were more options in terms of shipping rates compared to other e-commerce platforms we've used previously (Magento).
It takes some time getting your head around how to configure things but once you figure it out its pretty easy going from then onwards. We're using jetcommerces API integration feature which makes adding new features very simple as well since they have support available via their team members 24x7 / 7 days a week.