Compared to other reviews which compare the anime to its original material, I have not read any of Ito Junji's mangas and watched this anime with no expectations presented beforehand.
For me personally, I mainly enjoyed the second part of the anime (7-12 episodes), the ones prior either didn't seem that intriguing or all that enjoyable to indulge in, of course, I'm not saying that the stories were particularly bad, some of them were enjoyable, but most of them weren't that interesting.
The animation sometimes felt underwhelming especially in scenes where they were supposed to be crucial (i.e. Honored Ancestors and Supernatural Transfer Student for example).
There were stories which I really enjoyed, such as Painter (ep 9), Smashed (ep 12), Used Record (ep 7), and Town of No Roads (ep 7). Souichi's tales were also surprisingly amusing and enjoyable at times.
Overall I would give it a 6, some stories were very intriguing and some others were either not well done (animation-wise), or didn't seem that good from my perspective, but that is only my opinion.