Series Never lived up to its potencial
When I watched the first season of Merlin I thought "There are some contrived storylines and some rushed character development, but also a couple of good ideas, this might become a good show."
When I watched the second season I thought "Still contrived and often uses style over substance, but the last episodes where really good, it looks like the show is growing up."
When I watched the third season I thought "What the hell happened? You just can't change characters like you want without showing how they got to this point."
When the fourth season was on and the show still keep rehashing old plots I realized that it would never go anywhere. The last season I watched out of pure masochism, knowing that it would be the last and wanting to see it through. Well, I did, and knowing what I know now, I honestly rue that I started watching it in the first place. After the second, even after the third season it still could have become a great show. But the writers were too afraid to shake things up and so it died a slow, painful dead.
Series No matter how angry I get, Merlin is great
The characters are adorable. The acting is great. The subjects are sometimes deep. Its good taste increased, and, as of season 4, it is respectful and surprising. I love the characters and the part of this world it shows, and the finally justified convcoluted plots and character changes.
Series The average episode
As many I started to watch this because well, I like some saturday TV and Doctor Who was gone. Merlin is supposed to appeal to the same demographic, but after a while I realized this isn't quite the case.
I can summarize most of the episodes I caught in a single sentence: Some evil magic thing is trying to kill Arthur/Uther or otherwise ruin their lives and Merlin has to prevent this from happening without revealing that he is actually a wizard, 'cause that's forbidden. Merlin also has some sort of ultimate destiny but this is mostly foreshadowing that's not in a hurry.
Just knowing a vague synopsis of the Arthurian myths will take away a lot of the tension (guess who Arthur is marrying!) and the series seems reluctant to go too far from it's Status Quo or to have too much Character Development for it's leads. I'm rooting for Uther's death not because he's a Jerkass but because the show could use that. Until then I usually just see how well I can predict what's going to happen and count down to when a certain character smirks evilly.
While the acting is good and characters aren't unsympathetic, they've got some bad writing to carry. The dialogue isn't modern or properly old-fashioned, so we have a bunch of teenagers talking about who they "have feelings for", which makes me cringe more every time it's said, and quite a bit of the series' humour seems to be a bit on the childish side. The characters also like to overlook very obvious things when the plot demands it. For example: If you were close to a Jerkass king and wanted to kill his son, do you attempt to use slow and complicated magic schemes or stab the bastard and blame a servant? The writing goes medieval on the Rule Of Drama, stretching it until it can't stretch no more, even though most of the drama is a threat that's countered rather than furthering the plot.
The strength of the show is that it does have a nice atmosphere and can be entertaining, but if someone suggested a marathon I would run away. Merlin is watchable but not engaging, and really thinking about what's happening is not advised. I will continue watching it on occasion, but the show isn't clever enough to appeal to a big variety of demographics. I'd guess it'll be most enjoyed by people in their early teens.
Series Interesting premise, appalling execution
Pros: Great cast, good acting (especially Colin Morgan as Merlin).
Characters and relationships with plenty of room for growth.
A very promising setting.
Cons: Needlessly convoluted plots and a formula that repeats every season; no disturbing the status quo.
Blatant disregard of the horrors caused by Uther's Purge.
Endless harping on the two protagonists' alleged destiny to unite Albion and liberate magic, neither of which actually happened.
The writers' absolute refusal to have Merlin reveal his powers - which, ultimately, was the reason the whole plot went to hell.
The utter lack of respect the writers show towards every character except Arthur (and, by proxy, Gwen) : their relationships fail or lovers/families die, but they're either weirdly uncaring or their grief is irreverently exploited for the sake of the plot; they have no dreams, ambitions, or even much of a life except in relation to Arthur; disliking Arthur, regardless of whether it's justified or not, is a sure-fire ticket to villainisation and death.
Merlin and Arthur's relationship was pivotal to the plot: the great king and his trusted court sorcerer could never exist while Arthur continued to ignore Merlin's advice due to his being, quote, 'a worthless, idiotic servant.' But the creators' bizarre tactic for circumventing slash subtext led to their so-called friendship stagnating forever (Arthur alternates sneering disdain with complete indifference, while Merlin's inexplicably and unwaveringly loyal to the point of being both suicidal and homicidal), dragging the plot down along with it.
Arthur is selfish, immature, short-sighted, self-righteous and oblivious to the last; still practically a saint compared to his father, but not even remotely worthy of being lauded as 'The Once and Future King.'
Merlin's contradictory portrayal as "a nice guy who doesn't give a flying f**k about magic users," wherein he endorses the genocide of his own people on the word of an exceedingly dubious prophecy. Yet, this unrepentant traitor to both magic and magic users is apparently 'The Greatest Sorcerer of All Time.'
All of this means that most of the antagonists are far more sympathetic than the MC's.
= Why did I watch Merlin to the end? Stockholm Syndrome is probably the best explanation.