A Gnome developer, zdobersek, posted the first looks of how the Gamepad configuration tool in Gnome will look like. This feature is almost ready and also has passed the mid-term evaluation tests. Some screenshots:

As its quite impossible to support every device in the market, the user will have the freedom to reconfigure the device buttons if he/she finds them incorrectly mapped. The mappings are saved via  GSettings and reloaded every time the device is plugged in. Also, the user can report the mappings via Bugzilla, which will make it it a supported device list configuration. So the next time someone with a recognized device plugs it in , he/she will not have to go through reconfiguring the key mappings.

You can view the project's Gnome Live Page here.