This release is the final version of v2.1 Beta that was published on February 10th.
Below you will find the changes that were made:

Changes from v2.1 Feb10 Beta:
There is a one small change which is a breaking change for those who used the asynchronous invocation pattern using the "InvokeChannelAsync" or "InvokeAsync". (protected methods of ClientChannel)
This is a seldom used pattern so the chances of that affecting you are pretty minimal.
The change is very simple, instead of working with AsyncServiceInvokeCallback in these methods, it gets the general AsyncCallback which it then calls by passing it a ChannelInvokeAsyncResult which contains all the information needed.

Changes from v2.0: (These were included in the v2.1 Beta release too)

• New Output Caching module for Client Channel. (Useful feature, be sure to check it out in the showcases and see its documentation)
• New behavior attributes and extension elements (ActivationContextInitializerAttribute, ActivationContextExtensionBehaviorElement, ErrorContextHandlerExtensionElement)
• A userful commonly-needed synchronized (thread-safe) dictionary was added: SynchronizedDictionary
• Internal Optimizations and Mode Fixes. (Sequential channel management option work with asynchronous operations now)
• ChannelInvokeContext was made an extensible object
• Client Channel supports default single endpoint - No need to specify an endpoint name of the client endpoint in the configuration if there is only one for the specific contract
• Configuration-less services hosting API improvements
• When deriving from ClientChannel, you can override OnChannelFactoryCreated (new method) to apply anything you need.

Updated Showcases from v2.0: (These were updated in the v2.1 Beta release and were not updated since then)

• Miscellaneous - Configuration Section - A sample of the new Configuration Section
• ClientChannel - Basic - Simple comment indicating the ApplyBoosting can be set globally through the new configuration section.
• Services - Hosting - Simple comment indicating the ApplyBoosting can be set globally through the new configuration section.
• Services - Service Extensions - Simple comment indicating about the new behavior attributes and extension elements you can use to apply the extensions declarative or in configuration.
• Services - Service Error Logging - An example for attaching the behavior in the configuration using the new extension element was added.
• Client Channel - Output Caching - A new sample was added demonstrating the basic usage of the output caching