Another feature idea:
1. Block users: There are two settings. You can block users from private messaging you during chat (should you implement my idea of creating a private chat between two members) and/or you can block them in the chat so you cannot see any messages they post. In addition to that, any users you have on your ignore users list on the boards carries over in the chat.
2. If you get a PM during the chat in your inbox, a special message shows in the chat notifying you of the message. This notification is only visible by the user.
3. Allow users to view logs of the chat if the admin wants. Starting from the time the chat opens to the time it closes.
4. Speaking of closing times, admins can set opening and closing times for the chat room(s). They can do it in the AJAX admin panel in chat (a previous feature suggestion) or in the ACP. Once chat closes it displays a closing message and automatically kicks everyone from the room. If an admin is in the room at closing time, the admin will get a message asking to close the room or extend the time. Also, admins can close the chat room off preventing any new members from joining in.
5. The user profile should record how many seconds, minutes, hours, days a user has spent in the chat room in total time.
6. There should be an option allowing guests to view the chat and participate or not post, just view. Also, a cool feature would be to allow people to view the chat using an iframe. The chat could be posted using a similar code you would use to embed Google Calendar or Youtube videos.
IPS, if you want to offer a chat room, IMHO, you should create one that has tons of useful and dynamic features. Your other add ons are feature rich and dynamic. IP. Chat should be no different.