Main protagonist and antagonist are my major qualms with the show, but I thought everything else was great.
Most of the characters had interesting personalities and everyone was subjected to a lot of extreme situations. Most of the show came from seeing how differently people reacted to the incredibly fucked up world around them.
Between the child soldiers living under a mad dictator and the struggling natives that resort to terrorism, there isn't really a clear cut line of right and wrong in the show. When you force them against each other, it makes for some great, tragic character drama.
The highest point of the series for me was pretty much the entirety of Sarah's story, which I feel warrants special mention. Her role in the story is a living tragedy and it hits hard. I empathized with her as she suffered, rebelled, grieved, raged, learned to cope, and overall, just survived this nightmare she finds herself in. Perhaps her part is a bit melodramatic, but much of the series tends to play itself on extremes to stress the point. If you didn't feel anything while watching her story, you're either terribly jaded or just weren't paying attention.