Redirect Growl notifications to Notification Center (requires Growl to be installed).
So you've installed Mountain Lion with the all new Notification Center. Good for you!
But what's this? All those old Growl notifications mixed with the shiny and new. Doesn't seem right, eh?
Enter Mountain Growl!
Other solutions like Hiss are okay, but a actually a weird hack with a lot of down sides. So while waiting for Growl 2 (which hopefully will support the Notification Center) why not use the current Growl with a plugin that does the necessary. All as a 1st class citizen in Growl.