The following post is the result of some questions I received while proctoring for WCF hands on labs. I'm currently on the last day of some training in Seattle with Microsoft.
 
1) Transformation of messages
 
There is an  interface that allows for the message to be changed prior to processing - its IDispatchMessageFormatter. The following is a great article that may relate to questions about custom messaging processing (ETL like):
 
 
2) WCF Peformance
 
Here is a web cast on the topic:
 
 
3) WCF Security Fundemantals
 
Here is a web cast on the topic:
 
 
4) Thread Synchronisation
 
By default, WCF will establish an affinity between the service host and the synchronization context it was created on. On the www.idesign.net site there are plenty of resource downloads for other tricky threading situations.
 
6) Service Trace Utilities
 
There are two tools I have been referring to recently. The first is to analyze diagnostic traces (what is WCF doing on receipt of a single message) :
 
 
Channel 9 has a web-cast on the new Live Trace Viewer for tracing distributed calls:
 
 
7) Collections
 
Here is the link to a useful generic collection class for your operation contracts (something that you typically don't want to send over the wire):
 
See also this collection helper class: