TweetCaster brings a lot of functionality to the BlackBerry client world. Most people currently use Twitterberry, with UberTwitter climbing quickly (my choice currently). Well enter a new challenger.
TweetCaster does an excellent short video as an intro, showing off trends, searching and multiple Twitter account support toggling. URL shortening is there with TinyURL and picture sharing is integrated.
The application itself is from Handmark tha tmakes plentry of other BlackBerry applications, so they are not new to this platform development which gives them some credibility right away. You can get the client for free by singing in via Twitter on their site which sends a tweet you are trying the client. Then it is your to keep. A good way to use marketing balanced with a free client.