Haha I know what you mean. I didn't dare to watch Madoka at first either. Cute art with Magical girls was big push away. Then I heard about dark themes and was "Ok, let's see how dark it is. I bet it is... OMG! MORE!"
The first witch attack/animation is what made me go "Uuuuhhhh... nice!"
Since you saw Madoka I would recommend Steins;Gate as next since some themes are similar.