Nice. I've "eyeball metered" for years, sometimes don't even carry a meter (though now I have an app for my smartphone -- averaging, incident, spot, and "by rule" with 1/3 stop increments for film speed, aperture, and shutter speed). I completely agree; it's an indispensable skill (and well worth the effort to memorize a simple chart of how many stops below "Sunny" various common lighting conditions are). Eyes compensate very efficiently for reduced light, to the point where 6 stops can almost require a comparison (a window to look out of, for instance) to realize just how dim common workplace lighting is, so memorizing that simple chart (Overcast, for instance, is dimmer than you think, running 4-5 stops off Sunny) is effort well spent. Heck, print it and put copies in all your camera bags and cases, carry one in your wallet, etc.
Testing and knowing your actual shutter speeds goes along with this, hand in hand.