I loved the first half of the season and can't wait to see where things go from here. I was pretty surprised that they ended the first half where they did, and I'm very curious to see where we will be by the end of the season.
I think the main problem was, they caught up to production. When NBC gave the green light for the full season, they didn't have any more episodes on the shelf to air.
Thankfully, to echo the sentiments of others, it seems Charlie is in the process of growing up significantly. She's killed people, almost died herself, and has lost people close to her along the way. In a way, she's following in Miles' footsteps rather quickly...