Yesterday BBOS member olta777 had some news of a Blackberry native Twitter app in testing.
I have just seen on the Twitter boards that Vodafone is updating their version of a native twitter app called Vodafone Update App to be compatible with 5.0 OS's .
Right now the app is only being supported for the Blackberry Bold and Curve II devices. Sign in to your Twitter account and update your status, as well as your Facebook accounts. Post tweets, send and receive direct messages. Everything you need for a Twitter app including posting your photos to your social networks.
Here is Vodafone's link to their new Twitter App.
Vodafone Update App