Update: I actually had to change this so that it uses a LocalFeatureService with the EditorWidget. Here is the complete code:            ArcGISLocalFeatureLayer arcGISLocalFeatureLayer = null;
            LocalFeatureService lfs = new LocalFeatureService();
            lfs.Path = @"C:\Data\tactical.mpk";
            arcGISLocalFeatureLayer = new ArcGISLocalFeatureLayer(lfs, "Target");
            // Set the ID.
            arcGISLocalFeatureLayer.ID = "Target";
            arcGISLocalFeatureLayer.Editable = true;
            arcGISLocalFeatureLayer.ValidateEdits = true;
            arcGISLocalFeatureLayer.AutoSave = true;
            arcGISLocalFeatureLayer.MouseLeftButtonUp += new GraphicsLayer.MouseButtonEventHandler(arcGISLocalFeatureLayer_MouseLeftButtonUp);
            // Define a SimpleRenderer with a SimpleMarkerSymbol to display each observation. Each observation
            // will be a small red triangle.
            ESRI.ArcGIS.Client.SimpleRenderer mySimpleRenderer2 = new ESRI.ArcGIS.Client.SimpleRenderer();
            ESRI.ArcGIS.Client.Symbols.SimpleMarkerSymbol mySymbol2 = new ESRI.ArcGIS.Client.Symbols.SimpleMarkerSymbol();
            System.Windows.Media.SolidColorBrush defaultBrush2 = new System.Windows.Media.SolidColorBrush(System.Windows.Media.Color.FromArgb(255, 255, 0, 0)); //Red
            mySymbol2.Color = defaultBrush2;
            mySymbol2.Size = 8;
            mySymbol2.Style = ESRI.ArcGIS.Client.Symbols.SimpleMarkerSymbol.SimpleMarkerStyle.Triangle;
            mySimpleRenderer2.Symbol = mySymbol2;
            arcGISLocalFeatureLayer.Renderer = mySimpleRenderer2;
            arcGISLocalFeatureLayer.InitializationFailed += new System.EventHandler<System.EventArgs>(arcGISLocalFeatureLayer_InitializationFailed);
            arcGISLocalFeatureLayer.Initialize();
            // Add the local feature layer to the map. The map will handle the initialization of the layer.
            map.Layers.Add(arcGISLocalFeatureLayer);
             ESRI.ArcGIS.Client.Toolkit.EditorWidget editorWidget = null;
            this.editorWidget = new ESRI.ArcGIS.Client.Toolkit.EditorWidget();
            this.editorWidget.Margin = new Thickness(12, 50, 0, 0);
            this.editorWidget.Map = map;
            this.editorWidget.AutoSelect = true;
            this.editorWidget.AlwaysDisplayDefaultTemplates = true;
            this.editorWidget.VerticalAlignment = System.Windows.VerticalAlignment.Top;
            this.editorWidget.HorizontalAlignment = System.Windows.HorizontalAlignment.Right;
            this.editorWidget.ShowAttributesOnAdd = true;
            this.editorWidget.Loaded += new RoutedEventHandler(editorWidget_Loaded);
            this.editorWidget.DataContext = arcGISLocalFeatureLayer;
            this.editorWidget.LayerIDs = layerIDs;
            this.editorWidget.ApplyTemplate();
            LayoutRoot.Children.Add(editorWidget);
When the app starts I can see the EditorWidget with a set of tools for editing but as soon as the app finishes loading the EditorWidget reverts to a tool that allows you to just select, unselect, etc.