I use mine if Im taking macro stuff to zoom in for fine focus - and portrait stuff for fine focus.
I use it for the exposure simulator, if I want to see what the exposure will be like when in manual mode - saves me taken shots then knocking it down a few stops.
And I use it for self portraits with a mirror behind.
I use it for light painting by shining a torch where i want the focus, then painting the light.
Shall I go on?
I think the feature is excellent if you know how to use it, same as anything else when you learn to use it?