Is is possible to manage SQL Server 2008 databases via R2 Management Studio? Is it possible to manage SQL Server 2008 databases using SQL Server 2008 R2 Management Studio?
Yes, it is possible to use the SSMS from R2 to connect to a database server from any of the previous versions (I'm not sure about version pre SQL 2000, but it's not your case anyways).

You won't have all possible features activated (like Utility Explorer), but that shouldn't stop you to use it properly.