Previous versions of WCF only offered nested automated WSDL generation which can cause problems with 3rd party tools and other client stacks.
Flat WSDL is now an option for every WSDL/IMetadataExchange endpoint.
Learn more about the great productivity improvements to WCF 4.5 here: http://msdn.microsoft.com/en-us/library/dd456789(v=vs.110).aspx