I agree with Bub, I think it makes a big difference to the look of the car. Quite how much depends on the colour obviously, but on my denim blue - when it's clean - it looks great.
I have to be honest though that when I was looking at buying my A4 it wasn't something that even crossed my mind. Fortunately the car I bought had them fitted and it wasn't until afterwards when I saw other A4's without them that I realised what a difference it made. If I was to buy new, I'd definitely pay the extra to have them fitted.