The key thing is, if you really need an icon just make sure that it is simple, identifiable and consistent.

So true, but there’s one thing he leaves out here: learnable. Which, for me, usually means Tooltips. Too many Web designers in particular neglect these.

I’ve always avoided the word “intuitive,” since it points to an ideal that’s unattainable in many cases, especially for any complex application. Just look at the toolbars in most word processors; I defy anyone to “intuit” what all the arrows and boxes on the lesser-known menus do.

So it’s just a fact that not all icons can be instantly recognizable, but we can make decoding them easy. After that, if the factors quoted above are present, then learning proceeds smoothly. And that is often the best we can aim for.