I didn't have a high expectation for this show, but based on the trailers and the big names, I thought this would be an interesting show. However, It was actually more than what I was expecting. First, CGI is surprisingly well done. CGI on TV shows in general has a certain generic quality, but this show certainly surpassed the bar, and has convincing quality. The story is also very unique and well scripted. It shows more complicated story with deeper layers.
The downside is as some pointed out, it looks like it's rushed, or shorten the overall story. I felt there are at least two episodes missing. One between episode 3 and 4 and another one between 5 and 6. Also special effects have a wide room for improvement. They seemed to have focused on CGI a lot, but focused less on props such as severed limbs and blood.
I think people are giving this show lower ratings because of its gory scenes. I know not everyone has a stomach for it, but in my opinion, we actually saw less of Takashi Miike and more of Kdrama. Hope I can see more of Takashi Miike on season 2 if there is.