I developed a website for a client with very, very minimal needs. He doesn't sell anything online - he simply lists products and needed a more structured way to manage them than to edit a regular WP page constantly. Enter WP e-Commerce, the seemingly perfect solution. It's free, and with some editing, it does what he needs.
That said, we still have been unable to make the setting for 'no thumbnail cropping' work properly, so the users must pre-size all images before posting them. In addition, when we had a major issue due to an update installation, the only way to get actual support was to pay $47 for the 'Gold' upgrade, which entitled us to a single support request that took several days to get a response.
So if you're running a smallish business and know how to code, go for it. If you're doing anything that requires heavy lifting or you need serious support options, go for something more robust than this.