The VisualStates in the ControlTemplates of the RadButtons are modified. This may cause exceptions for users who have applied custom ControlTemplates for the RadButtons only in case they also set the IsBackgroundVisible property to False.
The ControlTemplate of the RadButtons is changed. The ButtonChrome element is removed to improve the templating mechanism of the controls. As a result, the controls will allow easier customization and maintenance with non-default themes and ControlTemplates. However, this shouldn't cause any backwards incompatibility issues for users who already use custom styles.