There are few joys in life like using something that is the perfect expression of its intent. Each trade has its representative tools, and their common trait is quality, even if it's not obvious to the casual observer, and often counterintuitive. The best tools in a category are almost always the least flashy, and rarely the ones a new practitioner would choose.
The Model M keyboard is like that: it's loud, ugly, heavy, and utterly lacking modern niceties like buttons to change your sound volume or check your email. And yet, it has that transcendent feeling that's hard to explain, that sense of rightness where you realize that you're using the best that's ever been made, that every change since then has been superfluous and cosmetic. With time, the loud clacking becomes the background music of your work, the harmony that tells you that your thoughts have become words. Its beige boxiness yields to elegant simplicity and the realization that true beauty is born of function, not appearance. The sheer weight of the thing turns to solidity and the confidence that it will stay where you put it. The dearth of features becomes the singleminded dedication to the parts that really matter and a proud disregard of unneeded distractions.
A tool attains its peak when a craftsman forgets that he's using it because it has become an extension of himself. Thus the humble Model M has become the iconic favorite of hackers everywhere, an ode to the engineers who grasped for excellence and acheived it.