I finished it yesterday at 2AM, after watching it all in one sitting. And, honestly? I can't remember 70% of what happened.
I do think that they had some cute moments - they have chemistry (nothing out of this world, but there's something there), and their scenes together were entertaining to watch.
I think maybe I was just bothered by the age difference between the actors? It's a pet peeve of mine, especially when one looks young-ish and you can tell that the other is in his thirties. Which is weird, because they're only 5 years apart - either Da Un's actor looks older than his age or Si Won's looks way younger. I honestly couldn't tell you. To me, it looked like a grown man hanging out with a college freshman.
I did like the first couple of episodes, they were funny and okay - but after that I just stopped taking notes.
Also, I didn't really get the hatred that Si Won felt towards Da Un?? Like yeah, I get it, you're poor and he's rich, but he hasn't done anything to appear as unlikable or snobby?? Da Un was always quite polite, even though I was expecting an incredibly smug rich asshole after reading the synopsis. He did annoy me when he asked his mom to choose Si Won's project when it wasn't even that good - I get that he was trying to help, but in what world did he think that was going to go over well?

And finally, I wish they had explored more with the theme of physical appearance, pretending to be someone you're not, being overly worried about how you look or how others perceive you, pretty privilege and the halo effect, etc. I thought that's what the entire series was going to focus on (and it kinda did, but not as much as I was expecting). I would've liked seeing Si Won relax and gradually stop putting on a facade, or seeing a different side to Da Un which wasn't as perfect as he was presented at first.