About my only usage is to augment my isearch. I frequently use isearch to navigate to a place on screen, but sometimes there are so many matches it would take a lot of repeated "C-s" to get there. I have "C-'" bound to avy-isearch (from within isearch), which instantly turns that into one or two keystrokes to filter down.

(or I could pick up the mouse, I know, but that's not why we're here)