I've run the Digital Musicians User Group in Boston in the past. The sad fact is, the only time where you can reasonably expect a good turn-out is when you have a big-name speaker (we've had one big-name producer and a few Berklee profs). All the other times, there were many empty seats. And we weren't even limited to a single DAW.
For anyone that does go for it, check out Focal Press's user group program. They'll give your group free books to give away each month (and they've got some great audio and music production books, including Bob Katz's seminal "Mastering Audio").
http://www.focalpress.com/usergroups/ They can also put you in touch with authors in your area who might be available to come and speak (which they've done for us).
Anyhow, our group fell apart when the company hosting us went belly up. Bakers, if you want to facilitate a user group, I would ardently suggest making it a music production group, rather than a Sonar user group. Then, you'll attract a bigger crowd and, perhaps, gain some new customers, rather than preach to the choir. Make it about music, not about technology, because music will always have a bigger fan base.