[takluyver]

This may depend on what you mean by 'proper production system'. It's definitely meant to complement, not replace Python modules, scripts and so on. I wouldn't write a web app in a notebook. But the LIGO team that discovered gravitational waves published a notebook demonstrating their data analysis.

I see it as useful where illustrating and explaining some computational steps is at least as important as executing them. Teaching is one obvious use case, but it's also valuable for sharing scientific methods, documenting a library with runnable examples, or presentations at programming conferences.