I thought they did a good job maintaining the central ambiguity of the premise. Is it just a trick, or is it really magic? I was unsure and thought it could go either way all the way up to the end. And I liked that there were plenty of things left unspoken. A very well-executed mystery story, I think.
And if late 1800s style men's facial hair were to come back into fashion, that wouldn't be a bad thing at all.