The notifier is fairly lightweight upon introduction, letting you select to receive updates from any list you choose, choose how long they will display, and where on your desktop they will show. And that's it! So it's not exactly trying to take away your attention from more robust AIR applications, like TweetDeck for Twitter.
If you don't mind the constant notification updates from FriendFeed, you can choose any of the lists you have preset, and individual notifications will pop up. Click on the notification, and you can be taken to the item, or click comment to start commenting on it.
A Pair of Notifications from the New FriendFeed App
The utility is likely best positioned for highly-targeted lists, say of close friends, family, or work. Otherwise, you've got yet another way to drink from a firehose. You can find the notifier here: http://friendfeed.com/settings/notifier. The company's official post is here: Get FriendFeed notifications on your desktop.