I am a hardware technician at a solar panel manufacturing facility and recently set up mumble/murmur on our network for use as an intercom system. The system works great...audio quality is perfect and the "attenuate audio while you talk" feature enables the music to be cut from the production floor PA while an announcement gets made.
Unfortunately there is one major issue, and that is that there doesn't seem to be a way to disable "Public Internet" from the server list in the Mumble client. That poses a significant security risk. Right now I am looking into work-arounds. If you want to vastly improve Mumble's client base I would find a way for the user to be able to edit the "Public Internet" categories out of the "connect to server" dialogue box.
Intercoms with high quality audio are pricey. Mumble not only has superior codecs and superior sound, but allows any desktop, laptop, tablet or phone to become an intercom terminal in a network. The intercom system I have set up sounds GREAT, comparable to systems that go for $10,000 - $20,000. I don't want this security issue to top us from using your software. If you can help with a work-around it would also be vastly appreciated, please email email@example.com if you have any suggestions. We are using Linux Lubuntu 12.10. Thanks!