I have to say that I'm very impressed with the detail that was put into this piece. The way the feathers look and where they were placed lends to the feeling like this is a scene from a dream. I also very much like the background; even if it's a little bit cliche with a dark angel in a cathedral.
I only noticed two off things and one was that the model looks like she's on a slight angle, while the wings look starkly flat against the background, not following with her movement.
The second being that the lighting on the model doesn't seem to match up with the light source to me. It looks like there's light coming from above while the only point of light is coming from beind her.
Other than those two things, this is a very lovely picture.