Hmm, I'm starting to think that I may just have very "different" taste when it comes to comedies/romantic comedies...

I actually really enjoyed this movie. The best scenes have already been mentioned by a few other users, so I won't go over them again... just provide commentary on the actors and their characters...
I thought Lee Dong Gun was really cute!, and, although his character, YoungBin, was a pretty terrible boyfriend, and I really don't think I could have put up for him as long as HaMi did, I somehow didn't get the feeling that he was being deliberately
malicious... for the
sake of being malicious. He treated HaMi well to a certain extent-- he was fun and impulsive, and he liked to be romantic-- but he had a lot of trouble letting her "really" into her life. He'd throw up his prickly shield immediately anything more "serious" happened, and then he'd regret the way it came out, and it was already too late.
As for Han Ji Hye, I LOVED her look. She looked absolutely gorgeous as she was running out in her "ancient" costume, and there was an adorable innocence about her that definitely
made HaMi believable and lovable-- despite her all-too-submissive personality.
I would say that the movie is definitely "lightweight"-- it glossed over the "details" of resolution... there are two significant timeleaps: one between their break-up and the airing of the commercial... and another between their "reconciliation" on the bus to the "way" the act "now"... as it's presented at the end of the movie. I don't think it was easy-- the journey to that point-- but we can see that both of them HAVE changed. HaMi is no longer painfully submissive-- she's the one playfully joking with YoungBin now about "breaking up" over trivial things... YoungBin treasures her. It's a short scene, but the change MUST be there... HaMi's cousin sort of alluded to it, too, in her outburst. I'm sure her cousin and her beau contributed to her little change of heart, no?
Essentially, I
could see why the two main characters fell for each other (well, aside from the abruptness of their relationship starting, I mean)... and, at least for the purposes of this movie, it seems as though love CAN make a man change. For the better. Realistic? Probably not. But, within the "boundaries" of this movie, believable. For me

Anyways, I think the trick to enjoying this movie is 1) not having seen the two leads in anything before (so that you don't have anything "better" to compare to) and 2) not treating it as true social commentary

But, on the other hand, I've seen a lot of comments about how this movie is just really "boring," so maybe I just have really strange taste...

Hehe, but I AM going to watch Sweet 18 now