Ask HN: Developer's e-commerce platform of choice? What works, what doesn't?

Note: I am currently developing an e-commerce platform, so this is both helpful to me and good for discussion. Ever since developing my first e-commerce site 10 years ago, it's been the focus of my attention and programming dreams (what, you don't dream about programming?) As important as this category of software is to business, and the tremendous market value it can generate, there is nothing out there I would use. We all know of Paul Graham's success story with Viaweb, and we also know where it ended up (Yahoo). Why hasn't there been more significant innovation in the e-commerce software space? The "cream of the crop" that I would refer to for discussion is: Magento, Shopify, Spree, BigCommerce, Volusion. I do not actually use any of these, and have always preferred to develop our software from the ground up due to the rather inflexible nature of each of these solutions. In your opinion, what is the best solution for web developers, other than "building it from scratch"? What features do you think are missing? What features do you think are well executed?