Re: 8X01 "Deep Breath" Grading/Discussion)(SPOILERS!)
Also, this feels like a strange thing to say, but I'm almost getting an early Tom Baker vibe from Capaldi. In his early stories like Robot and The Ark in Space, I got a similar feeling that this new Doctor was a bit unreliable, and potentially as frightening as the villain. Heck, in Robot, the Fourth Doctor has to be tricked into staying on Earth to help out.
I got a bit of that vibe too. Baker was the Doctor when I was a child and though I didn't see much of it, he used to scare me as much as the villains. The googly eyes and manic grin. I think it may be Capaldi's eyes that evoke the same sort of vibe for me.