Writing it in Java does have some advantages. One is that you can use the same code on a few popular platforms. Think about what that means to maintainability.
Please stop advocating this as an advantage, its exactly the opposite.
This is a advantage for the developer. For the users this is a clear disadvantage: It will never integrate as well into their platform as a native solution would. You might as well put on your projects web page that you care jack about your users.
Code is portable, User interfaces aren't. Take a hint from skype, implement your application in whatever language you please as a library and then make GUI's with the platforms native or best widget set. In their case that was C for the core and C++ QT, Delphi VLC and Obj-C Cocoa for linux, windows and mac respectively.