Reply 1997 - personal just because I couldn't stand it at all. I struggled to make it through the 6 or so episodes I saw, and the episodes are short! That's with dropping it, twice.
BoF - I enjoyed it but god, do I never hear the end of it. I didn't like the female lead, didn't really enjoy LMH in it even though I <3 him in everything else, it was too long, story was all over the place... eh. I only watched the entire thing because I was too new to Kdramas to drop one.