Regarding Renton's voice actor, Sanpei Yuuko just turned 20 when the series was finished, so I'm sure we will see progress from her in the future. In comparison to other recent mech series, Kokyo Shihen has got to be the best, as there is no whiny main character or predictable side characters. Music-wise, I thought they did very well to incorporate it where needed, though many people I know complain that the certain stretches where they play no music at all seem to bother them. But in my opinion, it makes it that much better.