I am part of a growing software project with at least 200 active developer in 10 locations. I would like to set up an on-line chat forum for developers because I think it would help to coordinate efforts. We have an email mailing list but I feel like some questions or announcements are too informal to send to everyone while mentioning it in a chat forum might be a useful community resource.

I have never participated in a software project that used an on-line chat forum so I would like to hear about peoples experiences. I am particularly interested in technical issues: Use of IRC vs. alternative platforms; how to manage access, eg. for developers only, allowing users to participate; the value of requiring certain announcements to be made on the chat forum eg who is resolving broken builds etc.

If I pitch the idea to the community I would like to have some good arguments why it would be a good idea and some prospective of its usefulness in other software projects.