I may have some time in the next few weeks to get us more organized on Meta. Becoming a user group looks relatively lightweight and I think we would qualify if we put in an application. Of course, anyone else who wants to curate the Meta pages and submit a user group application can do so!
If we start to do regular business, especially with people outside the immediate Wikimedia volunteer community or if we start to accept grant money, I think we should incorporate for liability protection and tax reporting reasons. Being an unincorporated nonprofit association that gets sued, such as because someone in our group made a copyright violation, would be bad. Also, incorporation may provide us more ability to get grants and in-kind contributions especially if we qualify for 501(c)(3). Incorporation is not difficult but it involves some time for applications to be created and processed. What gets tricky is selecting board members, drafting bylaws, and doing other necessary administrative work beyond the capacity of volunteers, so we'll need to think about that when the time comes. We are small enough now that all active participants could be board members, but if we scale to 30 members we will likely need an elected board. That is a good problem to have, and the Affiliations Committee can provide guidance for us throughout the organizing process.
http://nonprofit.about.com/od/faqsthebasics/f/unincorporationassociation.htm
https://meta.wikimedia.org/wiki/Affcom
Pine