Hard choice if it's to be a Chat OR Thread situation.
I like the chat because it allows for near-instant communication with people, no page refreshing, great for quick replies and you can keep an eye on the conversation while you are writing a message.
Down side to the chat is that it doesn't have a history, so things said half an hour ago could be lost to the ether ( what part is shown in the chat box anyways ).
I like the idea of a thread because you can communicate in it at your own pace and you can read back pretty much all of it. Down side of a thread is, if it's really active, you'll be doing a lot of page refreshing and you have no overview of things being said when you yourself are writing a post.