It has to be 10/10, because it's really outstanding in many ways. The casting is fantastic. Every single character has a meaningful role & is an integral part of the story. It's nice that the second male lead did not mess up the romance as it happens 99 out of 100 times in a kdrama. Based on her music videos & pictures that I've seen before I really underestimated Suzy. This is the first time I've seen her in a drama & oh man she is so cool, I'm super impressed. Also the actor that played Mr Choi was awesome, just like Strongwoman Do Bong Soon. The OST at first listen seems nothing special, but it fits really well, it just grew on me. In terms of cinematography it's definitely top tier among Kdramas, in this respect WYWS is way ahead of Pinocchio.

There are negatives too. Some of the "fake law" explanations were just too cheesy. There could have been more lighthearted scenes and the ending, which is the last 30 minutes could have been less rushed, should have been an hour long at least. Hong-joo's mom's shenanigans were really unnecessary too.

Personally I liked Pinocchio more, because I found the setting more interesting and it was funnier & the story flow was better & also the dramatic parts resonated with me more, but maybe I only feel this way, because I saw Pinocchio first and the two dramas are extremely similar in many ways. So yes, While You Were Sleeping will definitively not dethrone Goblin as the best drama I have ever seen, not even close, but it's a top tier work, that I will remember for a very long time & will rewatch it, in fact I might enjoy it even more the second time around, because some strongly hinted potential plot twists made me lightly frustrated the whole time...