The Firearm Blog has a video of a man shooting foster style slugs at 230 yards from a smooth bore shotgun offhand using the standard blade sight and compensating by guess. In the video you can see the trace of the slug as it arcs towards the target. You can't tell from the first part of the video, but the second part from the camera at the target shows that he's minute-of-scumbag for sure.
I recently fired some Brenneke slugs from a Mossberg 835 at 100 yards without as much luck, and the experience has piqued my interest. I never knew that slugs were worthy out past 100 yards; now I'll have to give it a shot (pun intended).