Now it's time for a little rant,
I know this anime ranks place 8 at the charts on this site, so probably there are a lot of people gonna disagree with me.
This rant will contain spoilers, so don't read any further if you don't wanna be spoiled.
It may be a bit sloppy, but I just wanna point some things out.
Ok, so we have the basic premise that Jintan suddenly is able to see a ghost of Menma, a ghost of a childhood friend. That is quite nice. You also get to know a lot about his other childhood friends, how they got drifted apart from each others and what problems they bear with the death of Menma. Still fine. Of course they think Jintan is crazy when he starts saying he can see Menma. So they screw around 8 from 11 episodes with believing him/not believing him. Well well. But I've got to point out that Menma as ghost can FREAKINGLY INTERACT WITH PHYSICAL OBJECTS. There may be some hesistation due to Jintan first thinking she is just a hallucination, but keeping that up for the most parts of the series is just downright stupid! She can eat (however that works, does she have to go to the toilet too?), she is able to write in her diary but not in other books (wth!? that makes no sense at all, if she can move the pen, she can write, WHY NOT!?)
When they finally found out that she actually can convince them by showing her presence in the last episodes (at least they do), the series becomes a bit better.
By the way: Later on Jintan admits his love to Menma, she is like. "Ya, I love you,too. And I wanna marry you. But uhm... on a second thought...see ya next live, I'm gonna reincarnate." There may be reasons, maybe she knows she cannot stay. But it's delivered in a strange way.
Otherwise the anime isn't that bad, the animation is ok, the music is nice and fitting, the characters have unique part (maybe Menma was a bit too one-sided though). There are some scenes that left a smile on my face, but the show never managed to hook me like e.g. Clannad. The story isn't awful either, but sometimes some details can ruin the complete show.
If you want to watch a kinda cute story about childhood friendship, mixed up with some rougher tones of drama,grief and selfish thoughts, there is a chance you aren't annoyed by the same problems with this series as I am and are able to enjoy it.