Now now.
Cersei definately is a piece of work.
But way i figure, shes is driven by a quest for power. Think about it, she was used by her father, her husband, just about every male in her family in a society that doesnt seem to value women's opinions that much. Now, she has this opportunity to throw her wieght around and hell yeah- shes's going to take it. She isnt stupid, just untrained and doesnt see the whole picture before she acts.
And She doesnt see people as human beings, just tools to an end. A lot like her father.
She loves/hates Jaime and her children. That is obvious, she has got a protective streak, twisted though it is. Cersei loves them , in part, because they are extensions of herself. CHild ren of her body and the twin brother/lover.
Jaime and Cersei are in love with the reflections of themselves in one another.
So, yeah, she isnt full of redeeming features,. But having her POV kind of makes me sorry for her, cause anyone displaying this sort of sociopathic behavior isnt going to come to a good end.

Just my two cents