Ok. There's a lot of character development, particularly with Cutty, Stringer Bell and Major Colvin.
Carcetti and the whole political side of things as well.
I forget which episode it is exactly, about 6 or 7, where the show suddenly takes off. Season 3 was my favorite until season 4, which I haven't finished but is already my favorite.
"There's never enough time to do all the nothing you want." -Calvin and Hobbes