A desktop client might make it easier to include certain features in the application that would be to difficult to implement in a browser. Perhaps coded in Java so that it is multi-platform? Also, if source code could be made available to expand the program might be an option to more easily create the desktop client, or expand the existing client in different ways (e.g. minimalist). You could even perhaps just provide an interface which other applications could connect to, which would also help promote your application.