I've told this account in various threads over the years, so if any of you remember it, please forgive the rehash.
For several years, I used to roll my eyes at the first Mondasian Cybermen, finding them almost laughable. I expressed this dismissal upon OutPost Gallifrey back in '05, almost mocking the "ski masks". One member, rather than getting angry, posted two words that made me totally reverse my opinion of that first design.
Suddenly, I envisioned a Clive Barker type nightmare. Imagine an operating theatre, one with the elevated gallery surrounding the perimeter. Upon the surgical table is a patient. His normal circulation bypassed, his blood being oxygenated and pumped by a compact heart/lung device on a cart next to him. His face is bandaged with sterile gauze and rather than conventional gas based anesthesia, the pain centers of his brain are nullified by a special "cap". His body temperature is regulated by a translucent polymer "suit", fluid filled tubes branching over the contours of his frame.
As a team of surgeons ready themselves for the arduous session ahead, the patient sits upright! He's seemingly conscious, but emotionally detached from his immediate condition. He staggers from the table and seizes the portable and self contained heart/lung mechanism, clutching it to his chest and he lumbers from the operating theatre as the medical staff stand around, far too shocked to consider restraining the patient!
Now, I'm not saying that's the actual "origin" of the Mondas Cybermen. As was stated in the original serial, the process was described as gradual, one organ after another replaced with artificial substitutes as the organic tissues failed. But the description "surgical gauze" brings to mind a medical operation gone horribly awry, patients alive only due to the hardware connected to them, effectively "lobotomized" but still driven by an insatiable will to survive, even if they can't recall the "little things" that make life enjoyable.
From that moment, I think I found the Mondas Cybermen the most disturbing of all.