The support. They are quick to respond, they provide excellent customer service (even when you are not a paying customer). The interface is easy to use and it feels like I have my own store. It can be hard to set up at first, so if you need help, there's no shortage of people willing to lend a hand. You have to have some technical knowledge to get everything working. If you're looking for more complex features you may want to look elsewhere. We are solving a problem with our students who need onsite instruction from an instructor and don't have access to such resources. This has solved that problem.