Daniel is a stereotypical 'American boy.' He's straightforward, friendly, somewhat simple, and has an aura of innocence (optimism?) that cannot be tainted by life's hardships. His innocence is different from Armand's or Claudia's in that Daniel is a child of modern America and he is a boy; there is no damp darkness that swirls beneath his soul. The baby of the vampire family (although technically the youngest is Jesse...), he is loved and watched-over by the older vampires (at least, up until QOD he is...). There's something loveable about him, despite his moodiness.
As an aside, I was blown away and amused by Daniel's courage or lack of sensitivity (who knows which it was...) when he had the nerve to tell Louis at the end of the interview that he wanted to become a vampire, too. *g* Poor Louis! After telling his heart-rending tale, to have this young pip-squeak say that he wanted to become this cursed being...! I had to laugh. Only Daniel... If it were anyone else, I'm sure he would have been dead in no time. Well, Louis wouldn't kill someone he knew, but Armand would definitely have had no problem in stepping in for Louis. You just can't hate Daniel--he's so...(blast it, no good translation for what I want to say) well, unconcerned, means no harm...whatever.
I had always maintained that Marius was the only one for Armand. Well, that certainly has changed and now I'm leaning towards Marius as Armand's ex. Who else but Daniel could make Armand laugh out loud? Daniel brought back fun into Armand's life and helped him take off his vampire mask.
A stroke of luck or a gift from God?
The hand of fate or devil's claws?
From below or saints above?
You come to me now
--"A stroke of luck" by Garbage
Sometimes I think the two are just good friends, all that lover stuff aside. At some point the line between friendship and love just became blurred.
Above all, Daniel's bright and simple outlook was probably astonishingly refreshing for Armand, who only knew to look for despair & darkness in everything. With Daniel, Armand could let down his load and be the young boy that he never was allowed to be.