Thanks to the shiny new Notification Center, you can customize the way incoming push notifications look in iOS 5. You can customize how many notifications display on your lockscreen, and you can even toggle the lockscreen view on and off
The three different Alert Styles allow to change the way that incoming push notifications display on your iPhone. You can have the new Banner view (that looks a lot like MobileNotifier), or the classic push view. You can also turn off Alert Styles entirely.
Overall, Apple is taking a much more thorough approach to settings and customization in iOS 5. And if you ask me, someone at Cupertino has been using a lot of jailbreak tweaks.