3D modeling software such as Rhinoceros (http://www.rhino3d.com/ http://www.rhino3d.com/) uses this model with great success and I'm sure there are others. The

3D modeling software such as Rhinoceros (http://www.rhino3d.com/ http://www.rhino3d.com/) uses this model with great success and I'm sure there are others. The program has a GUI that is very modular and customizable but the command-line interface is the primary interface. It takes a short while to get used to but after you do it scales very well as your experience grows. I have thought for a while that Photoshop/Illustrator would do well with a CLI but this is a compelling case for a contextual but system-wide implementation of this concept. The closest we have is Quicksilver or Alfred and while they are indispensable, making this part of the OS would open up some interesting possibilities.