osCommerce (or rather its newest version, 4) has a lot of features that will be suitable for small, medium, large / enterprise, and even global businesses.
It is free for its core version that on its own brings a lot: a fast shopping cart with a good checkout experience, sales and marketing tools, customer manager and order manager (including edit orders), support for multiple sale channels, advanced back end, many shipping and payment solutions, and more. Then come the apps, all 250+ of them. Free and paid, depending on what the business requires, they are easy to install via the back end.
osCommerce is mobile and SEO friendly too and can be scaled up to support databases with 1,000,000+ products and customers, and many thousands of orders a day. Review collected by and hosted on G2.com.
Nothing in particular. So far it was good. Review collected by and hosted on G2.com.