Has anybody tried it?
It does sound weird as an idea, but I just happened to do it while practising and it does get a dreamy tone that I couldn't achieve the normal way.
Dreamy combined to the soft slapping I like, that is.

So, wanna give it a try? Just follow the usual wrist motion but instead of getting the finger tip under the string, just get the nail.

The only thing that worries me is making easy things hard when using this technique. Oh, and, of course the possibility of doing damage to your nail.
[EDIT]
By the way, I can do it with my nails rather short, so long nails isn't a necessity.