Yeah building it up as a community forum is a lot better than just using it for support.
It can have a lotof benefits, people considering hosting with your company shouldnt be put off if they can see your current clients posting what they think of your company, at least they will know if they are satisfied with your service.
They will also see how you handle problems and how long until a problem is resolved.
Not every comment from your clients in your forum should be bad anyway
(i hope hehe)