Question

As an OO developer, maybe I have difficulty seeing its value. What added value do they give? Do they fit in an OO world?

Answer 1

Closures don’t give you any extra power.

Anything you can achieve with them you can achieve without them.

But they are very usable for making code more clear and readable.
And as we all know clean readable short code is a code that is easier to debug and contains fewer bugs.

Let me give you short Java example of possible usage:

    button.addActionListener(new ActionListener() {
        @Override public void actionPerformed(ActionEvent e) {
            System.out.println("Pressed");
        }
    });

Would be replaced (if Java had closures) with:

button.addActionListener( { System.out.println("Pressed"); } );