I love the show, but I'm an unabashedly male fan of Mecha Anime, so I might not be able to view the show in the same sense that you do. ^^;

I can say that Yoko is a pretty powerful character throughout the show. While she shows off quite a bit of fan service, she is also a lot more mature then most female characters in similar anime.

Again, this is all from my lenses, which I will admit, are glowing green with spiral energy at this point....