While it's better than the web UI, it suffers from the "mp3 player" problem of trying to make up its own widget library and UI style, and actually is kind of lame in a lot of ways (there is no top-level "new tweet" button, which is kind of a feature of all the mobile clients, and it's definitely a pain to use for DM conversations. It pops up weird non-standard shaped windows all over. I'd consider it a respectable indy effort, but pretty disappointing for Twitter, Inc.