I think online chat is one of those interesting tools - but not necessarily a very good one on conversion of those "leads" over to actual customers.

No, because half the time my site wouldn't have anyone on there to chat with customers...and if I'm doing something on the computer during the day chances are I don't have time to chat with people...though I think it's a great idea if you have a licensed assistant to monitor the chat for you. (licensed so they can answer real estate questions legally)