One warning about custom routes - at the moment any routes you register will take priority over Umbraco's own routes, so it's easy to break parts of Umbraco by registering general routes like {controller}/{action}.

That's changing, but until then you may want to replace the RegisterCustomRouteComposer in the documentation with this one, which puts your custom routes after Umbraco's routes.

[ComposeAfter(WebFinalComposer)]
public class RegisterCustomRouteComposer : IComposer 
{ 
  public void Compose(Composition composition)
  {
    composition.Components().Append<RegisterCustomRouteComponent>();
  }
}