He added a lot to the plot - though I have the feeling that the scene is a bit rushed, but I have seen it only once - and the look was downright creepy. Exactly what one would expect from a spokesman possessed by Sauron - a normal man (a Black Numenorean, I think, in the book) who conveyed the snarling and sneering that the bodiless Sauron could not do. In a way, it's like looking at Sauron himself.