Story 8/10
It starts really slow and sligthly confusing. I'd say this is the main downfall for the series, for those that do not find something about it that makes them want to stick with it. The first ten or so episodes are the weakest ones, but they ARE indeed important to develop the background and offer a starting point to the characters. At the end everything comes together nicely.
Art 7/10
I personally found the character designs appealing and distinctive enough. It handles its (I'm guessing) low budget well enough, but it lacks dynamic action, fluid animation or a visually captivating direction. But it gets the job done.
Sound 6/10
The music is good, not spectacular. Voice acting is very good, though you could find a particular character hamming it up from time to time.
Character 9/10
This is where the series shines. It's quite likely that you won't like some characters from the beginning, but them being initially unlikable really works positively for the series since their evolution and reasons for being how they are makes sense in a satisfying way.
Not all of them are particularly interesting, but the crucial ones are. By the end of it, they're people you want to cheer for.
Enjoyment 8/10
This is a very subjective area; I personally found myself enjoying the series more as it went on. It started pretty mediocre and confusing but as the episodes went by it found the right balance. In the end, the good taste left by the second half overcame the bitterness of the first one.
Overall 8/10
I'm a huge fan of sci-fi in many areas: books, movies and anime. In this last form of media in particular, I have enjoyed wildly different stuff, from Gundam to Getter Robo, with series like Votoms or Dougram in the middle. M3 has little resemblance to the real or super robot genre: it's definitely in line with what most of Evangelion talks about, but developed in a much simpler, easier to grasp manner. It's more akin to mystery series in which the characters' motives are the center, such as Higurashi no Naku Koro ni.
It was a pleasant surprise and I'm sad to discover most people did not find it appealing enough to stick with it until its final episode. What's more it was not commercially successful at all. While it clearly had flaws (slow start; mediocre production values; excessive use of flashbacks; an underdeveloped character), the positives outweigh the negatives and it offers a satisfying story with a clear finale and a more thoughtful focus.
