just found another Twitter-app: Tweetbook.
To be honest, really expensive (�4.99) but excellent app!
I love the push-notifications on my Home-screen (not seen before) and the portrait and landscape-mode. Great multimedia-mode. you can watch everything in-app (pics and wrbsite)
you can make pictures or upload the ones on your BB via Bridge.
Text from berryreview; TweetBook is made to look and feel like a native Twitter app for the PlayBook. With TweetBook, you get features such as the ability to search, browse, send images, send messages, and follow your interests and friends. Even when RIM does come out with a Twitter app for the PlayBook, features such as multiple account support are going to be what sets this app apart. TweetBook also takes advantage of the BlackBerry PlayBook’s built-in camera, allowing you to directly take and upload images to your tweet.