If you're new the genre, sageuk, new to KDrama in general, a fan of the actors or just plain bored - yes, do watch it.

You'll be rewarded by an excellent Park Bo Gum, annoying, funny or infuriating sidecharacters, an easy to follow plot, few dokidoki moments (thanks to our crownprince there) and a hilarious fatsuit (what? couldn't they find a single overweight actress in all of Korea? - is what i first thought but it seems this is part of a weightloss plot - meh...)
That said, about halfway through, the plot drags itself by mere threads, I found myself playing on my phone onstead of watching, skipping scenes and being bored by all the artificial drama with the queen and the ministers, later with her mom (who i found the least likeable charavter ever) and the family stuff. *yawn* not even Park could save me. I just wanted it over already.
Chemistry-wise...meh, 5/10. but whaddaya expect, she's a minor ffs....

so if your taste runs more deeply into the whole historcal Korea thing, you have more refined tastes about plot, character development and don't particularly care about the actors, skip this.

Tl;dr: cute faces, shallow plot, music was bleh, but was entertained enough, won't rewatch tho.