This was a great idea and the producers were clearly did their best. First, the good points, and there are a number of them:
1) Zombie effects were done quite well. This makes sense since it was apparently the same team as "All of Us are Dead" (hurry up with the next season!)
2) The storyline -- clearly difficult with an unscripted show -- was done really well, and the producers were clearly thinking cleverly while shooting went on to react to events and finished with a neat little denouement.
3) Some episodes' challenges were good and realistic for a zombie scenario -- finding items, rescuing survivors, finding working transport, etc., were done well and they were able to put little wrinkles on it with the unscripted nature that a scripted show would not have had.
4) Each contestant's character showed through their actions and narrative subtitles. This was good at inspiring fondness for some characters and dislike for others.
5) The contestants were clearly immersed enough to do things which hold some actual risk. Not hugely dangerous, but think things like jumping over barriers and climbing fairly high objects without nets/wires/etc., and "fighting" zombies (no stabbings or hammer strikes to the head, but definitely hard pushes, throws, etc.).
6) Tsuki is adorable.
Now, the bad points:
1) Obviously all the contestants knew they weren't in an actual zombie situation. Most were still able to act as though they were, but Rong-Chul in particular could not suppress a grin even during scenes that should have been intensely terrifying (well, except one that seemed to really shock him). Additionally, sometimes many of the actors were either overcome by silliness or made decisions they quite clearly would not have made during an actual zombie apocalypse.
2) While many of the challenges were pretty good, a couple of them also got into some silliness. Quiet (nonzombie) portions of the show also looked a lot more like variety talk shows than any kind of drama.
3) The survivors all being celebrities at themselves was a bit weird (at one point, a survivor even asks why there were so many celebrities clustered into the same country grocery store). It was even weirder when they tried to use their celebrity status to convince others they were trustworthy.
4) The presence of "NPCs" who served to guide events was a bit distracting. Early episodes handled this pretty well to do the initial setup, but some of the later NPC interactions were sort of blunt.
Overall, I enjoyed the show, though, and would look forward to another season.
