I voted for kind of cool, but pointless. It seems to be a good outlet for off-topic conversation, but for tea talk, the board serves the purpose. Trying to do tea chat in the IM isn't especially effective unless at least one other person is around to talk with. And even if people are around, they may not use the IM. Plus the IMs seem to get cleared out eventually (after 2 hours?), so unless you can get a response quickly from people online, you're better off posting to the board.
I think the IM might get more use if there were some set time for chatting. Not like you'd deactivate it all other times, just that there's some meeting time for chatting. If we all know that there's a planned chat session at say 8pm (state the time zone) every day, more people might make an effort to be around and chat if they're interested. I've come by when there's like 1 other person around, sometimes none. The chat's almost useless then. That's why I think scheduled chats might help give it more use.