I love the idea of the touchbar (that is, I'd get an external keyboard with one if it had the Fn keys too...).

I can think of a lot of uses for it, though maybe not making full use of the display capabilities. When I first saw it, I immediately thought "programmable ribbon controller".

Think of a virtual slider/fader that can output absolute position or relative movements, with (here's the kicker) the Fn keys selecting what the control is connected to.

For example, iTunes could use it for seeking position of the current audio. Tapping along the ribbon would drop you at that point of the audio (like moving and dropping the needle on a record). The Fn keys could switch it to Low, Mid and High EQs, let you scroll through your folders and playlists, etc...