This two-part finale exemplifies this series' chief virtues.
The Merlin Wiki covers both episodes here.
Number one, I feel good while watching it because every "white hat" acquits himself (or herself) admirably -- even Arthur, once he gets over his self-doubt. Let's see: We have Elyan, who doesn't crack until Morgana tortures him nearly to death; Gwaine, who, Klingon-like, fights nightly battles to obtain moldy scraps of food for his cell-mates; Gaius, who nobly turns down the aforementioned food so the knights can "keep their strength up"; and on and on and on. I'm of the firm belief that "family-friendly" entertainment should provide role models for its young viewers -- and The Sword in the Stone certainly does so in spades.
Number two, the retooling of the Excalibur story is quite clever. It's far more compelling - and truthfully human - for Arthur, after discovering Agravaine's treason and losing Camelot to Morgana, to suffer a crisis of confidence. And the fact that it is Merlin who nudges the young king out of his doldrums with a little magic and a lot of psychological insight fits the emotional core of the show quite marvelously. Above everything else, Merlin survives on the strength of the relationship between its male leads.
Number three, the writers once again strike an exquisite balance between drama and humor. It's hilarious to watch Merlin take advantage of his stupefaction spell, for example -- mainly because he never does anything truly mean-spirited to Arthur. And when Arthur "comes to" in the smugglers' camp and starts kicking Merlin until he gets a satisfactory explanation for his current circumstances? That's pretty funny, too. ("Why am I dressed like a village idiot?" LOL.)
And by the way, the bad guys have their interesting moments too. Agravaine's disgusted reaction to Morgana's excesses is particularly noteworthy. You would think he'd have noticed Morgana's attraction to pure cruelty by now. But perhaps - perhaps - he was blinded by love. That Agravaine seemed sincerely concerned for Morgana's well-being before he rode off in search of Arthur would seem to support such a thesis.
Also intriguing: The fact that Aithusa revives Morgana at the end. What could be the young dragon's motive, I wonder? Yes -- the writers obviously need Morgana to stay alive for season five, but what internal reason will they eventually offer? Personally, I can't wait to find out.
The script packs a dramatic punch, but it's also endearing enough to honor the fundamental personality of the show.
The performances are superb, though not 100% flawless.
A worthy king doesn't dwell on his mistakes. Instead, he learns from them and becomes wise.