The fact that I can customize everything I need (even more than the free version).
The fact that it has a lot of modules, so you can use as much or little one you want (and have an easy time choosing which to use)The simplicity in using the software (you don't have to have any previous experience in using the software to take advantage of all its features). It's not very simple to set up some modules (we needed to hire a professional to do this for us) but we have managed to get things working. It's been really useful in our organization because it allows each member of staff to access and modify the same file at the same time, without needing a lot of resources (especially since some sections are restricted only to the members who are responsible for them).