umbria - 7:33 pm on Aug 25, 2002 (gmt 0)

Icons are neither bad nor good. They're just another tool in your user interaction toolkit and can be used correctly or incorrectly.

Just to elaborate on a few excellent points above:

Somebody posted that a problem with icons is that the user has to decipher them - this is what human factors types call self apparency. It's more of a problem on websites than say an OS, because you may only visit a website once for a few minutes, rather than working with it every day.

As someone else suggested, you're reasonably safe with widely used icons such as envelopes for email and VCR style buttons for backwards and forwards. On this site, I'd say that the user profile and email icons in the forums are fairly well understood, but even here the designer has added text, so there's no confusion. The thread icon - a document with a purple star isn't so obvious.
The worst website icons are those in which the designer has decided to be clever and invent a whole new icon.