It seems like EVERYONE loved this show, it's possible that I could be nothing less than disappointed. And I was very disappointed. There were some positives, and I'll get those taken care of first.

Seo In Guk as Yoon Yoon Jae - I love him as an actor. He's got that cool, serious look about him; his smiles are few and far between, the intense stares always serve him well. I liked his character as whole. I loved when he realized he liked her, and his support of his brother, as well as his friendship with Kang Jun Hee were extremely special. SPOILER HERE - when he discovered that Jun Hee liked him, I really appreciated that he didn't treat him any differently and he still loved him as his friend, just as he had all along. END SPOILER.

Hoya as Kang Jun Hee - I don't know if it was the actor or the storyline that I liked in this instance, but I must say that this was my favorite story arc of the entire show. And I do not watch BL, so it wasn't due to that. He played the role with such sensitivity, and he valued his friendship with Yoon Jae, as well as Yoon Jae's happiness over his own. I'm so tired of characters that will do anything the can to get the person to like them, at the expense of the other person's happiness. To me, that's not love, that's obsession.

So, that's it on what I liked. On the other side of the coin:

Jung Eun Ji as Sung Shi Won - there was never a time in this entire show that I liked her character. She was pouty, immature and abrasive, and I couldn't understand why ANYONE would like her. Plus, I felt like she was playing the older brother, she didn't like him but still dated him. I could never tell when she started liking Yoon Jae, and even once she supposedly did, she was never nice to him.
Lee Si Eun as Bang Sung Jae - this character was irritating throughout the whole show.

Brothers and Shi Won storyline - older brother was just TOO old, so that storyline was creepy for me.

Lack of chemistry between the leads. Partially, this was due to their antagonistic love/hate relationship (which was not healthy, by the way), but I didn't see the attraction between them AT ALL.

Editing/poor differentiation between time periods - sometimes they told you what year it was, sometimes it was a small time period between the scenes, but I didn't think things ran cohesively through the story. For example, in one scene, they weren't even friends at that time, but he called her his girlfriend. She dragged him away, saying they needed to talk, and the next scene cut to something completely different. From what I could tell, the talk, where they would explain why he was calling her his girlfriend, never happened.

Language - I'll be honest, I don't understand why, even if curse words are used, they need to be translated. I don't like to hear them or read them. Men calling the girls B*tches - never a good thing.

Needless to say, I couldn't recommend this show to anyone, but I'm glad it was so famous, if for no other reason than to introduce others to Seo In Guk.