In my experience, FastSpring is a really easy to use, intuitive platform for selling SaaS and desktop software online. I tend to do lots of research before making decisions and we've been extremely happy over at FastSpring. It’s got all the functionality you need to avoid spending any significant development time, unlike a lot of other more basic solutions. And their customer service is outstanding - unlike anything I've experienced with other e-commerce vendors. I can see why they have such a happy and diverse user base. Very strongly recommended.