I'm going to keep it short.

This series has a very interesting plotline and interesting world which is what got me hooked in the first place. I think they execute it very well although some plotpoints could be explained better - but it did not bother me.
The cast is so great, i loved seeing every interaction between the side characters but also between the main characters. there wasn't a single moment where i was bored or indifferent towards what the characters were feeling. I felt very deeply for these characters and wanted so badly for them to have the happy end they wanted and deserved.
Go watch this!!! It's a classic and a staple K-drama for a good reason!!!