I love this name, but I'd never name a child with it, because it's hard to pronounce and it calls to get shortened to Nastia/Nastya which I don't like because it's too similar to "Nasty". She might even get picked on and called Nasty. And the other thing is people would always mistake it for Anastasia anyway. I'd rather see a child be called Anastasia, it poses far less problems for the child.
This is a very unique and pretty name! Like someone already pointed out, I found out about this name from the game Super Paper Mario, where a woman named Nastasia is one of the main villains :)