The power scale of Nightside seems a lot more fluid (and different) than Dresden Files, at least to my reading. I'd probably use another system I designed, Don't Rest Your Head, for Nightside.
Hmm... I have a copy (in fact, I think you gave it to me), but I'm not sure how well it really fits on a quick read through... the exhaustion/madness pool mechanic seems somewhat problematic.
There does seem to be a lot of emphasis placed upon power costing humanity, as far as it goes (Jessica Sorrow, for example), and Taylor's Undeserved Reputation trait is pretty overused.
Anyway, I just had an interesting character idea... an almost human Malvora white court vampire (those are the fear ones, right?). His bloodline is so degenerated that his demon can't even feed on other people - his abilities are powered by his
own fear.