According to Dr. Nick some long awaited improvements concerning WCF configuration come with .NET 4.0:
- short type names for configuration extensions : have you ever used strong naming and assembly versioning in your project (sure you have)? have you ever implemented a WCF extension (maybe you have)? did you ever have to always change your config files with every new project (assembly) version, because you had to use the assembly qualified type name - including version and token - in the WCF configuration (I did)?! Therefore you probably also added your extension in code only. That's why I love this new one.
- Channel factories with custom configuration: up to now you had two options for your WCF configuration (1. config file 2. create proxy the hard way in code). Now there's a third one (3. write your own serializable/persistable config OBJECT and pass it to channel factory).