These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Darrin was actually very insecure and felt the need for personal accomplishments to justify himself. It is notable that on several occasions Samantha's family hatched plans to grant Darrin magical powers so that he could better fit into the world of witches. But in the end he always rejected these in order to remain "normal". Interestingly, this was because he was shown to lack restraint when it came to the matter of misusing magic when he actually had access to it. Yet Samantha not only did he expect Samantha to exercise much greater restraint, but she very often actually did so.
Both actor Dick York and associate producer Richard Michaels have offered their own views on Darrin's feelings towards Samantha and her witchcraft. Michaels' opinion seems to be similar to that of the above mentioned, in that Darrin, "Was a square" and didn't want Sam to use her witchcraft because he didn't want her to embarrass him. York argued that Darrin didn't want anyone to find out about Sam being a witch because he didn't want others to try taking advantage of her and using her to fulfil their own gain, or even try and take her away from him (something that was explored in York's favorite episode, "I Confess").
It could be argued that Endora, Maurice and Samantha's other relatives had legitimate concerns about her marriage to Darrin. Given the much greater lifespan that witches and warlocks have, there was an obvious problem of how Samantha would cope with Darrin dying of old age in what was, to them, a very short amount of time. This concern also extended to their children, since a mortal child would likewise not live very long by witch standards. To them it might seem equivalent to marrying somebody who is dying of a terminal illness, and which could be spread to any children they have. Most grandparents would find the idea of their grandchildren dying long before they do horrifying. That is before one even factors in the idea that lacking magic is a handicap to their minds. Thus their desire for Tabitha and Adam to be a witch and warlock is not just Fantastic Racism, but genuine worry about how long they will live.
Complaining about Shows You Don't Watch: One of the biggest criticisms of the show was that Darrin should just let Samantha use her powers to benefit him instead of complaining about them. This was actually addressed many times in the show, usually with the explanation that Samantha herself wanted to live like a mortal (i.e. presents that Darrin worked hard to give her meant much more to her than something she could just poof up in an instant.) Added to that, every time Darrin tried to accept Samantha's powers, it usually would cause chaos (i.e. it would go to his head or someone would find out and blackmail Sam), so he actually was somewhat justified in not allowing her to use her magic.
There is also the issue of Sam being forced to be a housewife. Darrin was perfectly willing to help Sam with the housework, and this can be seen in multiple episodes. He just did not like her using magic. That said, Samantha came from a background where she did not have to do housework at all. There is a certain social class subtext here. It is like a very wealthy heiress marrying a middle class man. In fact, one wonders whether the rich ex-girlfriend that Darrin had would have consented to such a middle class lifestyle, or if she would have insisted on using her family money to fund something more lavish and how Darren would have dealt with that. It might have been the reason he did not marry her.
Uncle Arthur was only in about ten episodes, though some fans feel like he's been in more because Paul Lynde was so hysterical as him.
Harsher in Hindsight: Often times because of certain scheduling constraints, episodes of shows may be filmed/produced out of order. The first episode filmed when Dick Sargent played Darrin was, "Samantha's Better Halves,"; Dick Sargent once confessed that he felt uncomfortable with Samantha's line, "I only want one Darrin!" and even Elizabeth Montgomery said she was upset the writers put that in, considering the circumstances.
One early episode had an Imagine Spot in which Darrin imagines his future children with Sam, including a witch-daughter named Little Endora. If you consider "Passions" canon to the series, Sam and Darrin would later get a granddaughter named Endora.
Hypocrite: Darren. He strenuously objects to Samantha using witchcraft for anything, even just to make her domestic life easier. Yet he readily uses modern technological conveniences and even has a secretary!
Most Annoying Sound: Alice Pearce would sometimes use an excruciatingly screechy voice as Gladys Kravitz. Highlighted in one of Nick At Nite's ads for the show when they started airing the old black-and-white episodes.
Recycled Script: By the end of its run, the show was recycling its own scripts.
Seasonal Rot: The Dick Sargent episodes in particular are victims of this.
They Changed It, Now It Sucks: The "Tabitha" spin-off, among other things, retconning Adam to be a mortal (as well as Tabitha now being the younger sibling) despite the pilot showing him to be a warlock. Apparently, the original audience was also upset that Tabitha and Adam were suddenly adults.
Values Dissonance: Darrin's behavior seems remarkably jerkass and repressive to modern sensibilities. Depending on whom you ask, this was stepped up when Dick Sargent came on as Darrin.
In particular he seemed very hostile to the idea of Samantha acquiring a "career" as Queen of the Witches and states it in pretty much those terms, actually denouncing her comparison to the U.S. presidency on the grounds that no president has ever been a wife and mother.
Blink and you'll miss it, but in an underhand Larry proudly boasts they never should have let women vote. Kinda Harsher in Hindsight with so many political groups trying to curtail women's rights nowadays.