This IS the official RTM (Release to Market) Version.

If you want the latest patch level, also go to http://www.microsoft.com/en-us/download/details.aspx?id=30437 and download the appropriate service pack. You don't need the server back end to install the service pack. Run the correct file for your OS & hardware and it will update any SQL 2008 R2 components it finds on your system.