On it's own, yes, a vox humana generally isn't much to behold. However, when you mix it in with softer flues and strings, it can help to create a beautiful, almost ethereal sound. I'm used to them on theatre organs where, I think it is safe to say, they are a little more refined than their classical cousins. On the theatre organ, mixed with strings and tibia (tremulants on of course), they go a long way in creating a lush, warm tone.