I watched this ages ago. Thus:
1) I wasn't actually aware of who Joy was at the time and thought "Wow! She can sing." and was completely in awe. Her vocals are fantastic and yes, a quick Internet search told me who she was. Sorry for my ignorance haha.
2) I liked it a *lot* at the time since I was younger and hey, it is still a great k-drama. The main couple was so, so sweet and it had the "typical" events in a k-drama romance-- second love interest + jealousy, moments that are too cute (and cliche) to be realistic or relatable, misunderstandings + bad timing. It may be a bit frustrating to watch because c'mon get together already! but the ending is so fulfilling and rewarding.

I can easily rewatch this and I do find myself having the urge to... just for the warm feels.

I think it's ideal for new k-drama watchers or the audience who likes cheesy (but wonderful) shows but if you're not into romance or music much, I would say pass.