The ease of use, ability to get updates or new features when they become available with no additional fees! It's free up until you receive an invoice from them that is $50/month after which it becomes very expensive (though I understand why). They are constantly improving this software as well; however, some things still seem "unfinished" but don't let those disappointments discourage you! We have been using FMC since about 2013, though we were not 100% satisfied at first because there was so much missing functionality back then - now everything works great!! This program has helped us save time by providing our shipping department with all the tools needed to run their business efficiently and effectively without having to do manual labor tasks. They can manage multiple customers' orders while also allowing me to create custom email templates that look professional. And best yet.