Just installed it.
Some observations:
1) It only adds the contacts that are online to the phonebook. Unlike the other protocols that add the entire contact list. I like this FB plugin better
2) It does not display my FB name but rather my login email as the name when I send messages.
3) It occassionally resends all the messages in a conversation as if the other contact is the one sending all new messages. SO I sometimes get 10 messages I sent to them appearing as 10 new messages from them.

Otherwise loving it so far.