TUAW reviewed Netbot 1.0 a few weeks ago, and the app provides the familiar Tweetbot user interface to the ad-free and open alternative to Twitter. The update to Netbot 1.1 provides push notifications -- users can choose to receive notification of mentions, reposts, stars or follows. Tapbots built a handy Test Notification System button into the app, providing a way to insure that you're receiving notifications.
The other big new experimental feature is the addition of post search capabilities. From what I've seen so far, this feature works well. Tapbots also notes that they've added "various other fixes and improvements" to Netbot.