Goo Joon Pyo, the main spoiled, selfish, brat of the F4 is ultimately rewarded for being such a total jerk.
I hate that.

The lead girl, Geum Jan Di, was just not special enough for the F4 to be making such a fuss over her. She was constantly miserable, moping, uncommunicative, and wistful. She was hard to watch, slumping, stomping, and making weird faces. The kiss scenes were awkward and awful, and she managed to diminish what few feel-good moments there were, with her stiffness. Her character also makes stupid decisions at every opportunity.
I don't blame the young actress. The script was lame - but I hated her character.

Geum Jan Di's parents - while understandably meant to provide some comedy relief, were ridiculously over-the-top, and so goofy it made them unlikeable. Certainly unlovable. Geum Kang San, Jan Di's brother was great, and the little actor played his part admirably. I adored him.

So Yi Jung (the potter)'s story is actually quite workable, and he smoothed out any wrinkles with his fabulous acting, charisma, and charm. He did a great job, considering he didn't have much to work with. The very talented Kim Bum really rose to the occasion, and I loved his character.

Chu Ga Eul, the girl whom So Yi Jung eventually grew to love (once he'd finally worked out his issues), was a breath of fresh air. Honest, kind, enduring, and considerate. It was a straight-forward part to play, and the actress executed it admirably. I loved her.

Song Woo Bin, the mobster's son, had an embarrassingly underdeveloped back story. His character started nowhere, and ended nowhere. The entire character seems to have been an afterthought for visual effect, and a bit of rough. The actor did the best he could with the storyline, and managed to be both likable and believable.
I might have loved him, had he developed into a person. Failing a better script, options were limited. This is no fault of the actor, who did his job well. I liked him.

Yoon Ji Hoo, who was warm, kind, considerate, and steadfast ... was punished for his dazzling humanity by being given a storyline so sad and disheartening that the hopelessness of his very existence rivaled that of even Bidam (from Queen Seon Deok). The gut-punch of his storyline's ending was too much for me,
and I thoroughly hated it.

Ji Hoo himself, however, was a prince among men ... and I loved him dearly.
I've become a fan of the actor, and am starting to discover his musical talents, as well.
I was outraged by the final episode.

The music was tedious and much too loud. I was constantly adjusting the volume between blaring SONGS and modest dialogue. Watch it again? I'm too angry to answer that right now.

The F4's visuals, as well as the solidity, and dynamics, of their 4-way friendship was a big bonus in this drama.
It's a friendship I will never forget, and I feel privileged to have been a fly on the wall, watching this life-long friendship endure the hardships together. There were moments when I even liked the actress playing Jan Di, who was occasionally quite cute, and had a nice smile ... occasionally. The F4's true friendship endures the drama, and the half baked script. I loved the friendship.