I thought I'd mention that I, too, like the fact that we only see the things we need to see. Fewer special effects equates to more focus on the plot and character development. In a way I suppose it's like a book this way, since our brains supply the special effects. It just seems more elegant this way. FX can date a film; the lack of them contributes to a timeless quality. Also, we can't be disappointed by a cheesy effect that wasn't used.
My raising of this whole question was just an attempt at understanding how the writer intended for the flying to work, since what was shown (Eli's sweater) challenged my understanding. If we agreed it was an oversight, then I would dismiss the issue rather than trying to rationalize it as canon. But if Eli's wings are vestigial, then I'll keep that in mind as I write my fanfic (I've started it, but just barely).
