Microsoft has released WCF Data Services 5.3.0 with support for instance annotations in JSON payloads. It also provide support with which actions can be enabled for different types to have the same name and includes both serialization of actions with the same name as well as resolution of an action's binding parameter using the new IDataServiceActionResolver interface.
WCF Data Services 5.3.0 provides support for modifying the request URL in the OnStartProcessingRequest method. Moreover, service authors will be able to modify both the request URL as well as URLs for the various parts of a batch request.
According to official sources, support for instance annotations in Atom payloads will be included in the upcoming releases.
WCF Data Services 5.3.0 provides fixes for issues where code gen produces invalid code in VB, code gen fails when the precision facet is set on spatial and time properties and code gen was incorrectly generating the INotifyPropertyChanged interface code for subtypes in different namespaces. It also fixes an issue where odata.type was not written consistently in fullmetadata mode for JSON and where a valid form of Edm.DateTime could not be parsed.
The latest release of WCF Data Service also includes fixes for an issue where the WCF Data Services client would not send type names for open properties on insert/update and Execute() method fails for a particular payload with Data Service version 1.0.
WCF Data Services 5.3.0 also provides solution for a problem where type information was omitted in JSON fullmetadata payloads and open property type information was omitted in JSON update/insert requests.