Question: Are public folders supported in Exchange Server 2010?
Yes. Public folders are an included feature of Exchange Server 2010 and come with full support from Microsoft.
There has been some confusion about public folder support in the latest versions of Exchange. Microsoft began “de-emphasizing” public folders in Exchange Server 2007. The most obvious demonstration of this was the complete lack of a GUI administration tool for public folders. The Public Folder Management console was added in a service pack after some outcry from customers.
Exchange Server 2010 retains the same public folder capability and management tools as Exchange Server 2007 (with a few minor enhancements) and public folders are mandatory in some deployments (eg those with Outlook 2003 clients). Support for public folders will be provided for the full support life cycle of Exchange Server 2010.
However, the message from Microsoft is that if you don't need them, don't use them. And if you have a new need that public folders might provide, look to SharePoint or another solution instead.
Here is a table that the Microsoft Exchange Team published (in 2008) to help customers make these decisions.
From the admin perspective, since public folder migration can be a bit of a pain, I say if you don't need them then try to get rid of them for good.