Resolved with lib version 2014.2.0825.
With R2 2016 RadGridView will introduce ValidationType property that indicates what type of validation input should be processed(INotifyDataErrorInfo, IDataErrorInfo, DataAnnotations).
The problem will be fixed with Q3 2014 official version.
Add the "does not begin with" and "does not end with" to the list of filter parameters
The fix will be available with Q2 2015.
ArgumentNullException The fix will be included in LIB version 2015.3.1026.
Fixed for GroupRenderMode="Flat".
RadGridView's FooterRow is still part of the visual tree, even though its Visibility is set Collapsed.