I was going to challenge you, since I thought that was going to be the older http://theory.stanford.edu/~amitp/GameProgramming/AStarCompa... reference which I never found very helpful. The best intro I had to these was in a Game AI course and we basically implemented all these visualizations and more (bad screenshot: http://www.thejach.com/imgs/visibility_with_astar.png) to fully understand it. But the newer reference you linked is great and I'd agree it's the best public introduction.