This lens is brilliant, especially for video. Microcontrast is so good wide open.
For most video I'd take IS and a wider focal range over a wider aperture in a standard lens.
I can see where you're coming from, but I like the 18-35mm range and find that a fast lens can reduce the lights you need dramatically and it's not too weird shooting wide open on this lens as it's as sharp at f1.8 as it is at f5.6, at least toward the center of the frame. I also don't like IS much for video, especially on the wide end in which the jerky motion (optimized for stills rather than smooth video) becomes apparent. With a very long lens I can see its utility, but would argue for physical stabilization as preferable as it grants a more natural motion for video.
The last two shoots I was on used similar focal length zooms as the most versatile lenses in the kit (15-40mm t2.6 optimo and 17.5-35mm t2.8 lightweight primo, respectively, and obviously neither had IS!). Of course you need to switch to another lens for CUs, but I think I could get by with just this lens and a fast 85mm for an entire shoot. That the lens is near-parfocal with no breathing and impressive near-macro really makes it a compelling video lens.
However this is just personal preference and I can see the argument for a 24-105mm f4 IS being vastly more useful for anything shot with good light outdoors, for instance.