I vote not sure:
1) I, like Simon, spent many years in IRC and know how addictive it can be. I'm not sure I'd want the excuse to go down that line again! I spend enough time posting messages as it is
2) Some conversations in chat would replace threads which would have otherwise contained useful information which because they're in a chat rather than a thread will not be searchable by other people. Eg, someone asks how to take a dark frame in chat - that information will not be found by others searching later like it would have been in a thread.