Added some comments for myself later on :)

Author: Sam Storie

reactiveui-simple-user-control/SimpleApp/SimpleApp/App.xaml.cs

@@ -21,16 +21,19 @@ public partial class App : Application
     {
         public App()
         {
-            // This is the "magic" that automatically registers each view against the IViewFor<> 
-            //  interface it implements. This is specific to Splat, and could be replaced by the
-            //  specific capabilities of another IoC library
-            //
             var assembly = Assembly.GetExecutingAssembly();
             var builder = new ContainerBuilder();
 
+            // Since we're using the ReactiveUI.Autofac library this is all we need to do
+            //  to wire up our views and view models. Since it's based on Autofac we can
+            //  also freely inject any dependencies we've registered.
+            //
             builder.RegisterForReactiveUI(assembly);
             RxAppAutofacExtension.UseAutofacDependencyResolver(builder.Build());
 
+            // We've replaced Splat's default locator with the Autofac version so
+            //  we can continue to use the code shown in the ReactiveUI examples
+            //
             var view = (Views.MainWindow)Locator.CurrentMutable.GetService(typeof(IViewFor<MainWindowViewModel>));
             view.Show();
         }

reactiveui-simple-user-control/SimpleApp/SimpleApp/Views/MainWindow.xaml

@@ -20,6 +20,10 @@
             <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center" x:Name="CurrentValue" FontSize="48"></TextBlock>
         </DockPanel>
 
+        <!-- This is the "magic" that allows ViewModel-first controls to work.          -->
+        <!-- By using the VMVH from ReactiveUI we can let the library automatically     -->
+        <!-- resolve the required view for us. The downside is we seem to lose any      -->
+        <!-- design-time view of the actual control here in the parent window.          -->
         <reactiveUi:ViewModelViewHost Grid.Row="1" HorizontalContentAlignment="Stretch" VerticalContentAlignment="Stretch" x:Name="CounterViewModel"></reactiveUi:ViewModelViewHost>
     </Grid>
 </Window>