I'm not frequent fb chat user so I'm not quite sure if the chat in the stock fb client is really live or there is need to manually refresh. Notificiations works quite good. Even if the client is closed, it is still checking for new messages and notifications are showed everywhere - in the status bar, low power standby screen, events feed screen. Just add facebook account in the account settings. I think there is some problem with "chat and contacts" option in facebook account settings in N9 and i have this option turned off (probably because i read this advice here or somewhere...?). So the chat between more than 2 users is off. But chat between 2 users ("messages") is OK - if you were asking about multiuser chat, there was misunderstanding, sorry.