I'd actually love to use IRC... but we're just not confident that it'd work well for the non-technical people, and we need them to be able to get into the project chats and demo chats.
There's a plethora of IRC clients available, many of them very easy to use. No, you do not need to be a genius to be on IRC. Administrating channels (/mode and such) is a bit harder, but not everybody needs to do that.
We're experimenting with IRC at MyEdu; while it hasn't been awful for non-technical users, it's not necessarily great either. The above-mentioned HipChat seems like it could be more viable, so I'm adding it to the candidate list.
EDIT: Not primarily for remote working, granted, but for quick collaboration and some dev-related announcements.
Possibly we're selling them short here.