I'm a flutist (not a great one, but decent enough) so most VI flutes just don't sound very good to me. I must say, that you did quite a good job with this, and that it's very convincing. Still, I feel that something is missing that's needed to really push it past the point of sounding like it might be real, to sounding like it IS real. I think perhaps some breath noises (if possible) placed at the correct moments would do wonders for really fooling the listener into thinking it's real. I also don't think there's quite enough space during the places where a breath would be taken by a real player. Yes, a virtual flutist will never run out of breath, but some of what you have would be quite difficult to play for a real performer with the timing you have. I think this is the main problem. In other words, it needs to breath a little more.
Really beautiful piece. Probably any non flutist would be completely fooled into thinking it's the real thing.