This was just an all out good series. The sci-fi setting was totally realistic. The characters were totally believable and likable and had complex personalities. The technological details added depth and substance. This is the kind of realistic anime that you show a non-anime fan to prove that, even if they may not be able to appreciate the medium, they have to admit that the stories can have real substance and even rise above the best of their live-action counterparts.
It can seem slow at the beginning, but every episode ends with a bang in my opinion. And though the plot just seems to be episodic character-driven drama at first, later episodes reveal that there the story is taking a real direction after all.
The ending is natural and satisfying. This is just an all-around great show. Watch it!