Rated this one 10/10 initially, as I was hooked from the very start, and don't I love me some Seo In-guk? I sure do! Having Lee Soo-hyuk and Shin Do-hyun as part of the cast is a huge plus- loved their characters, and to be perfectly honest, I'd love seeing Soo-hyuk's beautiful face even if he were playing a statue. I did not exactly like Kang Tae-oh's character, but I enjoyed his acting, and will surely watch his future dramas too.
Can't really say why my rating changed to 8/10 by the end of the show: perhaps I took a bit too long of a break before watching the last two episodes, but some of the charm was lost for me near the end. Comparing Doom to some other shows I've seen in the meantime could have something to do with it too. Overall, this was a fun watch, though I could have done without some repetitious and unnecessary scenes.