There were a few initial concerns when we first heard about ARC. 

We were only piloting the program. This meant that there was no guarantee that we would keep using this program. It's hard to get excited about a program that may go away. 

In the beginning there was a lack of features, but this was only an initial concern as the updates and features are constantly changing. 

As we have moved passed the piloting stage, we still only have a limited number of licenses that are available. Right not the process for requesting Arc access is first come, first serve. It hasn't been a problem yet but it still makes people weary.