First of all, let me defend myself for giving this a 7 when so many people thought it deserved a perfect 10. I went into this anime with high expectations, which I knew at the time was dangerous, but even so I wanted to like it, I really did. It let me down for a few reasons:
By the time we reached the middle of the series the emotions were already at a very high level and, in the spirit of escalation, the writers tried so hard to keep ratcheting up the emotions that they spiraled out of control by the end. This is largely a matter of taste, I admit. But the crux of the problem was that I no longer believed the characters, they became characatures with whom I could no longer relate , and so I stopped empathizing with them. In particular, they were far too liberal with the crying. I am a firm believer that when a character cries, the viewer doesn't have to; when a character has every reason to cry but doesn't, the viewer will cry for that character. A few instances of tears well placed would have had far more effect on me than the shower of tears that they pushed on me. But again, that's my taste.
Related to this, the characters' behaviors/reactions were sometimes over the top. Not nearly as much as in a lot of similar anime I've seen, but that's not an excuse. (I rolled my eyes at the sexual tension between Jintan and Menma set up in the first episode, pulled straight off the top shelf of stock anime relationships, but thankfully it didn't last.) That said, despite some shortcomings, I thought the characters were fleshed out rather well, and they were the most endearing and memorable aspect of this anime for me (as well they should be!).
(2) Withholding of Information
In order to avoid spoilers I won't elaborate, but to those of you who have seen this already, you know what I'm refering to--or you should! I'm still angry at them for withholding one important piece of information in particular. Not only was this annoying and tantamount to cheating on the part of the writers (the viewer should always--with few exceptions--know the significant details that the protagonist knows), but again it prevented me from empathizing with the characters because I didn't know everything that they knew.
(3) Convenient Plot Holes
Again I won't elaborate, because I hate spoilers as much as you do, but suffice to say that the writers conveniently let some obvious possibilities slide in order to allow the plot to unravel how they intended. And in general, the characters just didn't ask the obvious questions that needed to be asked
The very basic premise is that Jintan (and all of them) are caught up in the past. Thus, it's very appropriate that Menma appears to him with the personality of the child that left them, that she never matured like the rest of them, even if her body did (kind of). She's caught in a bubble of time. I really liked the concept. But this all happened when they were very young. On a gut level, I couldn't buy that it would have affected them quite so deeply, or in the particular ways that this anime presented. It's difficult to describe what in particular bothered me without getting into spoiler territory, but suffice to say that while the concept was poignant, the execution just fell a little short for me.
I do recommend this anime, by the way, I just don't think it's deserving of the immense praise it's received. But in the end, the characters still made it worth it for me. Anjou/Anaru in particular was really well rendered, I thought. Her personality rang very true to me, and I could really empathize with her as a result. All of the characters stood their own quite well, even Jintan (I say "even" because it seems as if the protagonist in anime like this is always the most bland and uninteresting of the bunch).
I won't get into the sound/animation, etc., enough other reviews have covered that. I wanted to convey why I was disappointed, but I still encourage you to watch it if it sounds like your thing. (And enough people loved this, so I certainly don't want to rob you of that experience if you happen to be one of them!)