I haven't finished this drama yet. I watched it because I saw many good reviews about this, and I saw a teaser which was fun to watch. Personally I didn't like it...I watched up to episode 4, but stopped, my reasons are:
(WARNING: May contain spoilers)

Park Shin Hye terrible acting/ character
This drama is kinda old and her acting has definitely improved a lot! When I was watching it tho I always cringed at PSH, sometimes idrk if it's because of her naive shy vulnerable character or because it's her acting...
Her character is really annoying, it's so stupid and has no confidence what so ever, she needs to talk! I understand that it's because of her past bullying, but I can't deal with it anymore :(

The plot is confusing and not in depth
I don't get PSH character, maybe with more episodes I can understand her character better.
How did Oh Jin Rok fall for PSH from watching her pick up rubbish, I find that really stupid

Sorry for bad grammar.