This is an old drama, and I was extremely intrigued by the plot, so decided to give it a go. The first episode was quite confusing for me, the characters just come and go on in the screen, and no explanations are given as to who is whom. The overall pace of the drama was also a little slow. The editing was also quite jarred, so there were times when the scene cuts were very random. Also the way each episode ended was so annoying, with it stopping at one random scene, and that loud piano shaking the viewer out of their senses. Not necessary to end each episode with a loud BAM on the piano.
The acting, on the other hand, was superb. Top notch acting from all the actors. Yoo Ah In deserves special mention for the absolutely brilliant job that he's done here. The facial expressions of the actors while playing the piano were a bit too loud and exaggerated, but that's okay I guess... It's an old drama, and a melodrama at that. So this much leeway the show deserves I guess. Apart from the lead characters, the rest of the characters felt very unidimensional to me. They were just rich and bitchy. I was annoyed with the Seo family till the very end. Despite these flaws, the actors acted their parts well. No qualms on the acting department.
However, the main star of the show is its OST. It's very rare that k-drama OSTs are musically good. They are either too kpop-ish or they're just loud. But this one does such a brilliant job of maintaining the "Forbidden Affair" theme musically. The music is taut with tension, and so measured, and yet packs so much passion into it.
The ending of the drama was a bit meh, I didn't like the way it ended. The pace was also inconsistent, it got slow at parts, but it still managed to hold the attention of the audience. And that was just because of the OST that stringed each scene and character so well with the progress of the story.
Overall, watch it for the lead couple's acting, and for the interesting subject matter. The lead actors acted really well, and the director treated their romance with care and consideration. It never felt overtly raunchy or oedipal. A decent one time watch.