There were a lot of things that were done well in the show. The animation was quite beautiful and remained at a high quality all throughout. The music worked although they repeated some themes one too many times. The OP is pretty nice although I think others are better. The concepts they introduced in the first half of the series were quite interesting as well.
But a ton of problems arose as the series went on. The characterization was shallow, and this was surprising coming from BONES. Even at the end of the series, it's hard to sympathize with any of the main characters. The presentation was dramatic without being able to create any drama because the audience just never learns enough about anyone, even Akiyuki. The minor characters (especially Ishu and her crew) were there but you never feel like you know them that well either. When characters cried, I could barely understand why they were crying save for the part about Haru's mother. The most well-developed character was probably Nakiami, although she had less screentime than Haru.
Another issue was the world that Xam'd was set in. There is a war and there's apparently a North side and a South side but it never really matters because it's only ever important in relation to the military experiments with the Xam'd. I didn't care about any of the "suffering" or people affected by the war because it seemed to be there just to try to make the war more important. The military also makes a big deal out of the Humanforms, but those are pretty much useless in the grand scheme of things. In fact, many aspects of the show end up being pretty useless in the grand scheme of things including Ishu's postal ship, Ishu in general, Kakisu, Akiyuki's parents (who are shown in a ridiculous amount of scenes with absolutely no effect), and Raigyo.
There were so many interesting ideas and concepts, but the strangely dull presentation and slow pacing don't deliver them to their fullest potential. Everything up until about episode 14 was just fine, but it seems that every decision they made in the plot after that just contributed to less of anything being explained in the series. In my opinion, they should not have separated Akiyuki and Nakiami for the second half of the show.
It's bewildering to me how much I ended up disliking a lot of what happened in this series after such a charming first episode and beginning but I suppose BONES just hasn't been too successful with any of their original plots not based on a manga.
