Do not forget that for that extra $400 you not only get the "New" IS but you get weather sealing (which the 70-200 F2.8 does not have either) as well. The "New" IS is supposed to be good for up to 4 stops and I cannot say if that is true but I can say that I have gotten great shots as low as 1/60 handheld at the long end (though they are less common than blurry cam shots) on my 30D.


Also as great as the 70-20mm F/2.8 can be, take a few moments and think long and hard about how you are going to be using it. If you have any inclination to hike, or plan to handhold this focal length for long periods of time, remember that the F2.8 weights in around 1.3-1.5KG vs the F4 at .7-.75kg... Without camera body, lens caps, lens bag, or tripod ring....


I spent a week in Yosemite last year with my 70-200mm F4 IS, plus a couple of other shot focal lengths and I was caught short of breath more than a couple times on the Mist trail... I, personally, cannot justify the extra weight when I am hiking that the F2.8 would add.