There are two things you’re placing at odds: the speed at which you can slam your cursor against the left edge of the screen, and the speed at which your eye can actually make out text better because of proper whitespace.

I don’t think the two things have to be placed at odds, but if you say they have to be, then I’d argue that adequate whitespace (as shown in the WordPress and Gmail menus) is preferred over things like Fitt’s Law.

I admire gratuitous use of whitespace in application and website design. I don’t think most people are out to turn their users into the most efficient robots possible, shaving milliseconds off of the time that people can click the Spam folder in Gmail. Don’t be such an engineer. Aesthetics is a huge part of usability. Your demo proves a point but… it’s ugly. Fitt’s Law might apply to more labor-intensive interfaces (like the menus at the top of the screen in Mac OS X, which are constantly being accessed), but when an application is just one of many, or when (as in your demo) it’s just a blog with a few links, I think whitespace is a more important usability goal than Fitt’s Law.

Also, another thought: the “infinite edge” case doesn’t quite apply for touchscreen interfaces.

I have two monitors and have one to the left of my main browsing window. Interesting how that infinite edge disappears when I have to consciously stop in that space.

After I went and did this I saw that you noted the fullscreen mode was out of scope, but I thought I’d let you know the results anyway.

Thanks for the write-up. It’s a very interesting thought – definitely something to consider when designing navigation. Multi-monitor situations are another interesting case for this, but I’m guessing isn’t common enough to stress over.

FWIW, Opera (I tested v. 10) seems to be compatible with this “law” too.