Ok, so since this anime is a collection of short stories, I'm gonna be rating them individually and later calculating the average score for the entire show. So, without further ado:
Ningen Shikkaku - 8
This was the opening story and I thought it was well executed. It showed the darkness of the human heart and mind living with disregard for its own life. A very real depiction of depression, as you will. Not only that, but a very sad representation of Dazai Osamu's own convoluted life... This one was the longest (with 6 episodes), but it didn't felt dragged out. It's one the largest novels of the bunch, anyway, and the most recognizable.
Sakura no Mori no Mankai no Shita - 4
Definetely the worst of the bunch... I haven't read all of the books these short stories were based on, but this was the one that made little to no sense to me. From beggining to end the tone was all over the place, with over-the-top comedy and serious f'ed up murder, the story and characters made little sense, and even what I could gather to understand of it seemed to be told in a very "Meh" kind of way, with no cohesion to it. Maybe, for people who have read the book, the story it's actually good? Who knows? But I didn't like it, and the great soundtrack didn't managed to save it.
Kokoro - 8
People I know who read the book claim this wasn't very faithful to the original story or, at the very least, was missing a lot of details, which made the overall understanding and message of the story very partial and incomplete. But, besides all of that, I still enjoyed the "Kokoro" short story and how it was done with two different perspectives towards something similar. The characters may be a little shallow since we don't get much background like in the book, but it was incredibly enjoyable seeing it as a tragic love story.
Run, Melos! - 10
Definetely the best of the bunch. It was extremely well made and not even one of the others could top it... The characters were great, the music was great, the visuals were great, the setting was great, and the storytelling was superb. This was astonishingly visually telling, with an incredible setting of performing arts in a very believable theatre environment. And it also showed a cheerier side of Dasai Osamu's Life. Truly, a masterpiece!
Kumo no Ito - 8
Really liked this one. It revolves around a simple concept: "everyone deserves a second chance to do good, but they have to choose to". Great symbolism, nice music, and a very pitiful character... Loved what they did in such a small time.
Jigokuhen - 6
It picks up as another story from Ryunosuke Akutagawa, but this time it tells a more complex, and historical, story than in Kumo no Ito (apparently). I loved the visuals during this one, but that's mostly it for me. The story was nice, but it felt convoluted and I didn't really pick up the symbolisms by the end. But, even with all of that, I still enjoyed it quite a bit.
So, all in all, it comes down to a 7.3, so I'll give it a 7. It was a pretty enjoyable experience. I recommend you watch and get your own conclusions, and I hope you'll enjoy it.