WS-Trust and WS-SecureConversation were updated today. WSE 2.0 implements these specifications, not the older versions, so they are required reading if you working with the related features in WSE 2.0.
One of the most notable changes to WS-SecureConversation from a WSE perspective is the removal of the KeysXml element in a SecurityContextToken. As a result of this change, WSE 2.0 no longer supports 3-party Secure Conversation out-of-the-box - there is no interoperable mechanism for carrying the required key material. Instead, custom additions are required to the built-in SCT to make this work.