As a fan of the Lord of the Rings, Arwen is immediately associated with it in my mind. It's a beautiful name, but I would be hesitant to use it because it is so heavily associated with LotR (and I say that even as a fan.) I don't think it's unusable for someone who's not a fan, but you should be aware that most people will automatically link it to LotR.
There is Anwen, which is similar and doesn't have the association. But then I think Anwen runs the risk of being mistaken for an Arwen.