Ultimately the OMPC will come with a graphical user interface. The purpose of this GUI is to make the experience nicer and closer to a other similar packages. Some people might be scared of the console window.
The second reason to create a GUI instead of using console is to make it possible to let windows update (animate) while you are using the console. This is how it looks at the moment.
I am a big fan of Tkinter and its recent updates in the version 8.5 (actually Tk's). Tkinter is light and if you learn it you realize that you can do anything that all the other toolkits like wxPython or PyQt can do (look at http://sk1project.org/ and the screenshots).