I really like to work with people from different areas as you learn alot about the different views to an application. In my case it is the contact to the developers while testing and then the contact to the users while training them.
There is also a great synergy between those two areas. First you test the new system or features which are implemented. While you test you learn alot about the application and the process. And this is the perfect basis to teach others. Then while teaching you get alot of feedback what users need and what they do not like. This feedback you can then give to the developers or concept team.