As many said before me, gunslinger girl is a drama series. If you're expecting action, look somewhere else. If you have seen the trailer, you watched most of the action scenes in the show, if I recall corectly.
The focus of the series is the interactions between the girls themselves and the firls and their fratellos ("brother").
I've also noticed hints of fear of growing up , uncertainty and so on. The last two episodes are beautiful, but I heard that the second series ruins it all from more people than just Aion, so I guess that mus be true.
I'll watch the second series eventually anyway, out of curiosity, but it's far from the top of my list though.