Everybody that has hosted Exchange 2010 running using the /hosting switch knows it is a real painful experience. It is difficult to implement, it is difficult to maintain and there quite a lot of functionality missing like UM, Public Folders, the Exchange Management Console and integration with other products like Lync Server 2010 or Sharepoint Server 2010.
There has been a lot of complaints from hosters about this situation at Microsoft and Microsoft had to make a painful decision: Microsoft will no longer invest in the /hosting version of Exchange Server 2010 and it will be discontinued in the next version of Exchange Server (code name Exchange 15).
Jaap Wesselius 