I used to be a big fan of Public Folders back in the Exchange 4-5.5 days. That was before SharePoint Team Services v1 came along. Since then I have been designing collaboration solutions entirely in SharePoint products and technologies. The only thing that was missing in providing an end to end solution was archiving email discussions (3^rd parties solved the offline requirements). So now that WSS can archive emails, there was talk of Exchange dropping support for Public Folders. This blog http://msexchangeteam.com/archive/2006/02/20/419994.aspx