I've always felt that opening the forums to non-customers would be very helpful. I had a lot of questions before signing on, but in most cases, the answers were available here. If you fear that the boards will get too crowded, make most of the forums "read only" for non-customers (but give non-customers their own forum in which they can ask questions).

As for the structure, I think it's mostly okay as is. You might want to break up "Residential Service" into a few sub-forums, such as sign-up, features, trouble-shooting, wish lists, etc.