Great news for notification junkies: you can throw out all the third-party hacks which let you pipe your Growl alerts into Mountain Lion's Notification Center. Now Growl itself has been updated to V2.0 and had native integration with OS X's notifications. Better yet, it adds support for forwarding alerts to iOS services Prowl and Boxcar.
We have covered several third-party add-ons to make Growl play nice with Notifications. Now you can forget those, update Growl from the Mac App Store and tell it to forward any or all alerts to the built-in system.
This effectively lets any Growl-enabled app work with Mountain Lion, with no effort from the developers. Well, almost: If they want their app's icon to show up in Notification Center instead of the Growl icon, they'll need to upgrade their app using the new 2.0 Growl API.
But the biggest news for many is the inclusion of BoxCar and Prowl. Both of these let you push notifications from your Mac to your iOS device. Previously they were display style plugins. Now you can pick, say, Prowl as an action and use another display style of your choice.
This doesn't actually change the behavior, but it keeps the back end neater and easier to understand. Also, Prowl users will need to generate an API key to use this (it's easy, it can be done from the app, and you need nothing but your Prowl username and password).
The update is free for all existing users.