I am currently using the Sigma 70-200 F2.8 APO with my 1Ds and for the most part I have been happy with it, however it is not an IS lens and I am finding that my hands are getting a bit shakier these days. I do a lot of portraiture where I want to blur the background and keep the eyes crystal sharp, and I think a max aperture of F4 would still give me some of that.
I have considered the Canon L 2.8 version also, but I would just as soon do without the extra weight. Has anyone used any of these lenses comparatively that would care to make a recommendation. I figure that the F4 IS lens would get me a couple of extra stops (shutter speed wise) over the Sigma, and I am hoping the optics would be more pleasing. From what I've read, the boquet on the Canon F4 is considered fairly pleasing.
Any opinions?