Well, here's something I thought we would never see -- a minor update for Twitter for Mac, which finally brings Notification Center support to the client. You know, it only took just shy of 10 months after the release of OS X 10.8 Mountain Lion for that to happen. The 2.2.1 update also fixes Growl notifications in Lion and Mountain Lion and squashes several other bugs. But reviews are already coming in saying that the Growl fix doesn't work.
Yes, Twitter for Mac was updated in April, but it languished for a couple years (Twitter for Mac 2.1 was released in May 2011 with a minor update