Few things. URLs should automatically link like they do on the forum. If I just paste an http link, it doesn't turn into a clickable link.
The swear filter doesn't work. The rude word beginning with S that's another word for "crap" on here is filtered, yet on the chat, it's not. Maybe setting it as a user-selectable option in the Admin CP would be a nice idea, since some sites might want the forum to be clean, but allow some leeway in the chatroom.
This might be quite hard to do, but I'd like to see the possibility to make it run off an existing IRC channel in place of...whatever it's running off now. The IRC option might have to bypass some things (eg, no bbcode), but overall I think it would be quite useful, especially for sites run on restrictive shared hosting. Since, after all, anyone can make their own channel on a network like, say, Rizon.
I realise the first two points aren't critical though, since, after all, it is a beta. :P