There is an interesting opinion over at Bokardo.com. Joshua Porter writes that labels are better than icons. This is interesting because for icons are usually a neater way to convey what a button does or where a link leads. Now there is an example which shows that this is not always true: The icons are not providing any help, so Joshua Porter claims that labels are better.
My conclusion is: If you use icons, make sure that there are really easy to understand. Otherwise, use labels. Or even better, use both. If a user got accustomed to a functionality, the label can later be reduced, as I will show in another blog post.