Adaptation Displacement- Most people have never even heard of the "Cyborg" novel, or the fact Caidin wrote three sequels, none of which had any connection with the TV series.
And those who did read the novels after only being familiar with the series were often surprised at how violent Caidin's version of Steve Austin was. For example, his bionic arm was often referred to as a deadly bludgeon. And there was a poison dart gun in his bionic fingertip.
Also in the novels, Steve's artificial eye was merely a camera. Steve couldn't actually use it to see anything. Oscar Goldman even commented, "Only God can restore lost sight."
Aside from the dart gun, there were additional differences in Austin's bionics; he had a radio antenna built into a rib, a secret compartment for gear in one of his legs, a steel-reinforced skull, and in the novels Austin's bionic arm was his left. Also, while on TV the term "bionic" was used in the singular, as in "bionic arm", Caidin's books used the awkward (but more grammatically correct) plural form, so "bionics arm".
With the exception of of the eye being just a camera, the novelizations of various episodes that were published incorporated the Martin Caidin version of the character, resulting in stories that were more violent than their TV counterparts. A notable example is "Love Song for Tanya" which ends with the villain being apprehended on TV, but in the novel, Steve uses the poison dart gun in his arm to kill the man.
Awesome Moment: For fans, too many to count, though many point to the ending of the first hour-long episode "Population Zero", in which Steve javelins a metal pole through a van, as one of the first examples.
Fridge Logic: Backstories for Steve or Jamie commonly proclaim that bionic implantation "saved their lives", yet none of their physically-enhanced body parts (limbs, eye, ear) are crucial to sustaining life.
However after the transplants many episodes depict how damage to bionic limbs can be life-threatening to Steve and Jamie.
In the novel Cyborg on which the TV series was based, Steve Austin not only lost 3 of his limbs and an eye in the crash, his heart was also badly damaged. His life was saved by a bionic heart valve.
They could be speaking metaphorically. While their injuries, once stabilized, weren't life-threatening, the loss of multiple limbs and other organs would have been a serious liability to pursuing anything resembling a 'normal' life (certainly in The '70s, before handicap accessibility was the law of the land). For vital, athletic people like Steve (test pilot and astronaut) and Jamie (professional tennis player and amateur skydiver) there's a huge psychological factor involved (this would have been true with anyone but even moreso in their cases). Indeed, in the original pilot film, Austin at one point attempts suicide.
"Holy Shit!" Quotient: The crash footage in the opening credits is still disturbing after all these years, primarily because it was actual footage of a real crash in which a test pilot was catastrophically injured - but he never got the bionics.
Also, anytime a robot-disguised-as-a-human is unmasked.
Narm: "Sweet Jaime" as sung by Lee Majors in "The Bionic Woman" (the two-part episode that introduced her). Oh dear. (It doesn't help that the melody is loosely based around the show's theme song.)
Also, Bigfoot was known to scare more than a few kids.
Also in the title sequence with the footage from Austin's lift body plane's on board camera of his fateful crash seconds before impact is frightening to see obviously he is going to hit the ground hard. And it isn't special effects; this is actual in-cockpit footage of a real crash. It must have been especially Nightmare Fuel-ish to test pilot Bruce Peterson, whose spectacular crash was featured in the opening credits. Imagine reliving that week after week. (Reportedly, Peterson was not a fan.)
Marty Stu - Col. Steve Austin. He's very different in the novel, and he and Goldman hated each other there.
Justified in that he pretty much had to have been at the peak of physical and mental performance in order to have been an astronaut (especially back then, when nearly all astronauts were originally military pilots with advanced engineering degrees).
Recycled Script - not so much in Six Mil itself, but several scripts from this series were later remade for the first season The Bionic Woman due to the spinoff being commissioned on very short notice.
Retroactive Recognition: In "The Return of the Six-Million-Dollar Man and the Bionic Woman", Dr. Shepherd, who performed life-saving surgery on Steve's son Michael, was played by a young Bryan Cranston.
Kate Mason, the second Bionic Woman in "Bionic Showdown", is played by future Oscar-winner Sandra Bullock.
Special Effect Failure: In "Killer Wind," though they used wind machines to indicate an oncoming storm, they didn't cover up the conspicuously sunny and cloudless skies.
An often-cited failure occurs in one episode where Steve throws a bunch of large tires at a group of mooks. One of the tires splits during the sequence, revealing the styrofoam within.
Although there were a few moments where doing so was actually effective (such as the famous training run sequence from the pilot film that became an iconic part of the opening credits), showing Steve running at full speed often came across as looking silly on screen. This was realized early on; inspired by the use of slow motion to denote power and strength by NFL Films in its filming of football games, the same process was introduced by the producers to depict Steve's bionics in action. Once the slo-mo was introduced, the only time Steve was shown running at full speed was for comedic effect.