Is this the IS or non-IS version?


I'm drooling over the idea of getting the 70-200 f/4 as my next lens (I have the 17-55 f/2.8 IS), but I'm not sure if I need the IS or not. I would mostly be shooting landscapes and portraits or candids. Not technically stuff that requires IS, but it's always nice to have, right? It's also a big difference in price. If I consider getting the f/4 IS, I know I'll be tempted to get the f/2.8 non-IS instead, cause it's very close in price. argh.