My previous post spent over 600 words knocking down the Exception Handling Block, but version 3 and higher does have one nice feature: WCF Exception Shielding. This allows exceptions received by a WCF service to be mapped to Fault Contracts.
Exception shielding is important in order to hide internal implementation details from service consumers. This can make your service easier to use and, more importantly, prevent exposing sensitive internal information in your exceptions.
Enterprise Library Exception Shielding seems to be a good use of configuration to decouple a service interface from the underlying implementation.