Windows Server AppFabric provides a premier hosting environment for hosting your WCF services. As Windows Server AppFabric is built on top of/extends IIS 7 and Windows Process Activation Services (WAS), you get all the benefits of this proven hosting platform plus a number of features designed specifically for working with WCF (and WF) services.
Windows Server AppFabric provides an intuitive user experience that allows you to set common WCF knobs without having to resort to complex XML configuration. For example, once you've deployed an application consisting of one or more WCF services, you can configure common settings such as whether to expose metadata, set up monitoring and tracing, enable the service(s) to start automatically, and configure throttling to ensure that demand can keep pace with available resources.
Also, as working with WCF services is very different than a typical website or ASP.NET application, Windows Server AppFabric recognizes these differences...