Illustrator single style live inner shadow

If you stack a transparent stroke on top of an offset blurred stroke, you can achieve a pretty spiffy Inner shadow effect if you enable "Knockout group" on the object level in the appearance panel.

See the full image for a view of the actual appearance panel.

Extra tweaking can be done by adding a live "offset path" filter to the shadow-stroke.

*edit* now with the proper screenshot-attachment, fully expanded layer style! *edit*