Blackberry development platforms
Visual Studio is a RAD development tool that makes it easy to link some code and put together a few screens, but you don't get much control over what happens and you can't easily customize it.
I prefer Eclipse as you can access the RIM API and you have a lot more control over what happens, for example. create your own controls, customize menus, and get much more functionality in your handset.
In various forums http://www.blackberryforums.com/developer-forum/ orhttp://supportforums.blackberry.com/rim/board?board.id=java_dev for example you get much better Java support (Eclipse or JDE).
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I am using Eclipse because the initial setup for Blackberry development and video from RIM assumes you are using Eclipse. Since you need a Blackberry JRE and it will be tested with a Blackberry simulator, using Eclipse will be the easiest. Visual Studio is beautiful, but not free (unless you are a student and visit the Microsoft Dreamspark website)