As discussed in the article, one of the useful consequences of Fitts Law applied to the mouse cursor is the usefulness of UI elements on the sides and in the corners of the screen. Clicking on a target tucked into the corner is ostensibly much easier than a target elsewhere because you can just "toss" your cursor into the corner, click, and know the target was acquired.
It's a great idea, but I fear it faulters due to lack of user education. Maybe I'm just an idiot, but even when it seemed possible to toss the mouse to get what I wanted, it took explicit knowledge of that ability before I learned to take advantage of it. Even though the Mac's menu bar is always at the top of the screen—put there solely to take advantage of Fitts' Law—I still creep my mouse up to click in the middle of a menu title. The first feature that really felt intuitively on the edge to me was the Mac OS X Dock, and that's why the Dock (or dock-like things, like DragThing) feels fast and efficient to me.
Part of the problem is the style of the graphics. Especially in MS Windows, it's difficult to make a clickable thing flush with the edge or corner because it'd look weird. As the article mentions, the original Windows Start button was helpfully in the corner, but was surrounded with a border of dead (unclickable) pixels. This made the Start button behave intuitively as it appeared (like a button with a border), but ruined the opportunity to throw the mouse. The newer green Start button is flush with the corner, and even if you switch back to a classic appearance, the border is still clickable, even though it doesn't appear clickable.
So it's a little disconcerting that the slick new Office maximized window elements, such as the Office Button in the top left and the Quick Access Toolbar along the top, are still rendered with a border, even though you can click all the way to the edge. I'm hoping that MS's extensive usability testing has found that people clicking sloppily get the benefit of Fitts' Law without having to know how it works. But from personal experience, the border seems likely to train users to creep up to the target anyway, leaving the "click anywhere" trick to be a power user effect, to be written about in Office tips books and practiced like keyboard shortcuts.
