I absolutely adored this saeguk. I binged it in almost 3 days. The concept is fascinatingly original, the characters and plot deliciously mature, I'd say there's almost no part of this show that was unnecessary (something very rare in Kdramas). I practically started watching bcz everyone was hating it despite the unusual plot summary (I have no idea why'd people not admire a well-made project like this). It has some veteran actors in their best forms playing some of the best developed characters. The king and the mother-in-law of the Jo family were flawless.
In fact, it has one of the finest negative characters I've seen in a while. And she's a smart, wise, plotting woman who is infinitely complex as a character to simply be a villain. I loved that dialogue when she said, "Must you disappoint me till the end?" She literally savored the death of her husband! And Rowoon's character improved with every episode. I loved how frank Jung Woo is. He confessed multiple times, and with such heart! It's a beautiful, thoughtful drama. The exaggerated comedy complemented the dark assassination plots. I actually enjoyed how childlike our hero is, his innocence never undermined his courage. And Sun Duk is such a mature character, I loved how she listened to the encounter of the princess and Jung Woo, I don't think the expression of love can get any more profound. I loved how Jung Woo mentioned his remark to his father as cruel. Those are bits of life. The matchmaking of lady Yoeju too was fine in its deductive finesse, it was a display of strategy at its finest. Lady Sam Soon was a literal delight. I wasn't fond of all the pairings (I'd have liked the farmer to fall for Doo Ri, it was so predetermined I wished they'd show that people don't always fall in love with who they're supposed to be with. The 14-year-old prince and 24-year-old lady Ha Na was another daring move. I don't know if 14-year-old kids actually fall for older women like this or vice versa especially considering how grown-up Ha Na is and how mature her taste is) but at this point I'd rather not complain (and it all worked out in the end like pieces coming together in a puzzle).
Could not find a single plot hole in the drama till the end. And I have to mention the playful music and stunning visuals. The interiors were especially detailed. The pingfengs (folding screens) in every room were so pretty and distinct (I especially liked the mother-in-law's minimalist and the princess's maximalist flower-patterned screens). In a way they reflected the personality of the inhabitants. There were also indicative cinematography, pretty visuals and nice locations (probably common in every high budget saeguk, so I digress).
The ending was fitting, wise, not shocking but reassuring and very proper. I loved it. I think the last I contemplated rating a Kdrama 9 was 'Flower of Evil' and even that didn't have a perfect ending. This was a well written, well-acted and well executed drama, which managed to strike the right balance between light and dark and remained warm till the end.