Partly because of Invertalon and all his pics (!!), yesterday I found a local place with the lens in stock and I bought it. Last night, I covered a charity gala and this morning a marathon. In both cases, I exclusively used my 5D Mk III with the 70-200 2.8 II and the 24-70 II lenses. Besides the obvious difference in focal lengths, I'm seriously hard pressed to tell the difference in PQ, focus accuracy, color/contrast, or general wonderfullness of pictures. Granted, I'm not pouring over the photos looking for similarities or disimiliarities. But still.
And I find I'm not missing IS either. I shot at some pretty slow shutter speeds last night during the gala, and all was good. I will try to find some time to post photos after the weekend (and after I've processed and submitted them to the newspaper).
The bonus is that I don't know if I need primes for low light anymore. Changing lenses when you're shooting stuff for a paper is a total hassle, no doubt about it, and the 5D Mk III really deals beautifully with high ISOs. And you know, you can get some prety decent background blur with this lens. So I may be selling off some primes soon (to help cover the really, really high cost of the 24-70).
I know, I know, a post like this is nothing without pics. But I'm off to shoot more stuff right now, and don't have the time. Hopefully soon.