This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
It is possible for a J2ME application to run on a Blackberry and a Samsung mobile; although the Blackberry may require extra steps. You should look for the Java ME platform/API support each device. This will help you determine which devices your application will run on.
Something to consider with the 8100, BB devices have proprietary APIs which allow you to leverage more of the device.