My favorite Twitter app ever is Birdfeed, a "very nice Twitter client." It was built by Buzz Andersen and it was indeed very nice. After using the new Twitter app, I think we need a very nice Twitter client more than ever.
Buzz sold Birdfeed to Brizzly, who rebranded it as Brizzly for iPhone—much like Tweetie became the official Twitter app after it was purchased by Twitter—before Brizzly was bought by AOL. The app became less nice, and now you can't get it at all.
Full disclosure: Buzz has made me delicious cocktails before and I really enjoyed drinking them.