I'm extremely surprised that this is getting so much praise, nearly as surprised that I did not drop this early on around EP 4-5. I think my biggest gripe is that up till episode 7-ish there was nothing but pain & suffering. I realize that this is a melodrama, but in order for me to feel the value of this genre, in order to feel a sense of loss the characters' lives need to be introduced before everything went to oblivion for them. I'm giving this a 5 instead of a 1, because the main leads had great chemistry and the acting on their part was outstanding and their romance was well written too I guess. The cinematography was decent & the OST is quite memorable too. Usually I like the 16 episode format, because the writers don't have a chance to overdo fillers & they can just freely use their best ideas to full effect, there is no need to hold back for further seasons, but here I felt that 16 episodes were too condensed for all this borderline sadistic writing. That's not all, there were so many characters I felt apathetic about. Mr Shifty-eyes Architect, or that CEO? that always shouts, why did I have to see his pointless attempts at romance, just why? I like Kang HanNa, but her character made little sense to me, so I guess her acting talent might've been wasted here.
I've been reading the comments under the final episode & everyone was like "Thank God it's a happy ending, like this it's 10/10" etc, but I'm just not that forgiving. Literally 5 minutes of moderate happiness before the ending credits isn't enough to forget all the bad things, feels like the writer was pressured into changing her originally planned ending too.. Naturally there is no way that I would ever rewatch this drama. On the upside watching good melos mess me up for quite a while, but since I did not become emotionally invested in this one I'm already over it :-)

edit: For reasons unknown I kept missing the show, so after rewatching it I liked it a lot more than for the first time, so changing my rating to 6.5 stars. :-)

edit2 (a year later): I'm looking at this review that I've written and it feels surreal that I gave this 5/10 the first time around. Changing the score once more! .-)