This was the first drama I watched that introduced me to K-dramas, so it remains one of the most memorable (I'll admit the nostalgia gives some bias to my opinions)

Pros
o Visual FX in this drama were implemented beautifully with AR sections of the show, and make this show unique.
o The OST is one of the best things about the show, with notable songs by AILEE, Elaine, and Loco + U Sung Eun. Star (Little Prince) is still a great listen, and made me stick through outros. Even instrumental music was executed well, and gave scenes good vibes.
o I enjoyed the story, and the complications the VR had for players. Every scene involving AR had my total attention. The relationship
for the leads was a steady progression which was meaningful by the end.
o All the associates for Jin-Woo's company, the friends of Jin-Woo & Hee-Joo contributed to the story, and had satisfying character development. None of the characters felt like filler for the sake of the story, and I got emotional for lots of them.

Cons
o The acting at times wasn't groundbreaking for the leads, but moments of greatness shined through near the end of the show.
o Character development was pretty stagnant. I had hoped for more complexity for Jin-Woo, and Hee-Joo to have a more significant role alongside Jin-Woo (instead of being sidelined for lots of the conflicts). Both leads were one-dimensional for parts of the show, and I wanted Jin-Woo to be less stoic and Hee-Joo to be more willful.
o I'm one of many to feel this way, but the ending of this show left a hole in me that still hasn't been filled. I would've preferred no possibility of him being alive or them exploring more of the game. Still holding out for a second season in my dreams, which resolves this cliffhanger ending.