Available for download is the list of breaking changes between beta 1 and beta 2 for WCF and WF. To save you some time, here's my condensed version of the list.

• When adding site or machine-level collections of behaviors, those behaviors will be merged with service-level behavior configurations of the same name. Previously, you would only get the behaviors configured directly by the application if there was a naming conflict.
• The blob encoder was renamed to the byte stream encoder. It still works the same though. Put some bytes in one end and the exact same bytes come out the other end.
• The local "in app domain" transport channel was removed. Use named pipes instead; they're just as fast and have been available for years.
• A security feature involving SAML tokens that you've probably never heard of has very slightly changed its default behavior.