Microsoft Entourage 2008 for Mac, Web Services Edition is a required upgrade if you are using Exchange Server 2010. Entourage 2008 (without EWS) uses WebDAV to communicate with Exchange Server and WebDAV has been removed from Exchange Server 2010. Entourage EWS now uses Exchange Web Services (EWS) as the primary protocol for communicating with Exchange Server. This means that Entourage now can potentially access all the information available through EWS.
So what about Public Folders? According to the Entourage EWS documentation Entourage can now access Public Folders, but there is no mention of whether Entourage needs Public Folders. Entourage without EWS did absolutely need Public Folders. During Exchange Server 2007 installation you got a question; Do you have any client computers running Outlook 2003 and earlier or Entourage in your organization? If you answered yes; a public folder database would be created. If you answered now; no public folders in your organization. Since Entourage EWS now can access free/busy data through EWS there should be no reason to continue having Public Folders in your Exchange organization. But I have been unable to clearly determine if that is the case. Right now I think it is unnecessary, but I will do some further testing.