My favourite 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.