The purpose of the tool is to allow the user to create and build a custom image as well as enabling parameters of the build to be configured.
I've tried to apply the principle of least surprise and tried to make the app fit in on a Gnome desktop by following their HIG. One possibly unexpected outcome of this is that you modify Preferences which equate to values in local.conf
There are several issues with the GUI as is that I will be working on next, as well as some extra features that I am intending to implement in the coming weeks.
There's even a Yocto bugzilla component for the 'image creator': http://bugzilla.yoctoproject.org/buglist.cgi?product=Build%20System&component=image%20creator&resolution=---