Originally when I picked up this manga I expected it to be a little bit more Hunger Games. I was pleasantly surprised to find that it was not. If anything, it's somewhere between your average fight-based YA dystopian novel and X-Men with a good dash of Doctor Who for time travel fun.
Time travel, surprisingly, drives this fast-paced manga. There's the survival elements, of course, but the idea of changing the present so that an ill future can be avoided definitely is at the foundation of the story. It's still a shounen action manga - lots of psychic powers and fight scenes.
The art is easy to follow. I didn't have near as much trouble as with Trigun. Good character deisgn and ideas as well.
The characters' names are difficult for me to remember but by the end I could distinguish between them fairly well. The use of scars in character design helped me to distinguish between appearances. I absolutely loved the kids. (Marie's adult character design and the cheap jokes that were made at her expense bugged me, however)
My main two quibbles with the characters, though, are: (1) the underuse of Oboro (maybe because the manga was cancelled?) and (2) there are so many that each individual character is not as memorable for it despite having memorable groups of characters. (The children for example) They're good - but they don't have individuality. Ah, well. You can't have everything.