I bought this before I went travelling in the middle east, where I thought that the harsh sun could cause problems with my photos. Sure enough, it proved it's worth, and makes it all that little bit harder for the lens to get damaged from scratching onto something. Another added bonus is that it acts as a lower gear when using manual focus, which is far too sensitive on the AF-S 18-55 without it, almost unusably so I thought. However, with this hood, I could make the fractional degree movements necessary to change focus on such a poorly designed manual focus (I know it's not intended for manual use, but hey).
If none of the above sounded useful to you, then save the £20 and buy some more memory or something.