I\'ve looked everywhere and just can\'t find a way to launch the Rate and Review from my app. Does anyone know how to launch this task on the new Windows Phone 8.1?
I can confirm that the method posted by user3496220 is working but only if you are using app id of your app from Dev Center (not CurrentApp.AppId)
Like this in your case:
await Windows.System.Launcher.LaunchUriAsync(
new Uri("ms-windows-store:reviewapp?appid=fc0c29fc-f615-4753-aad7-5cf760ca5d2d"));