Any reason you need IS for that 70-200 f/4? I don't have it on mine, and I haven't missed it. Then again, 90% of my images use a tripod.
If you hand hold (event shooter), then the IS is priceless. Especially at the longer focal lengths! Will also help negate (to some degree) the slower apperature by allowing one to use slower shutter speeds.
But...but...If you use IS, then you're going to be able to reduce/eliminate camera-shake blur, but not necessarily motion blur. You might get away with handholding at 1/15 sec., but you're still going to capture any movement within that time.
I recently shot an indoor play with my 70-200mm f/4 (non-IS), and I don't think I would have come out with better images had I utilized IS. Just something else to think about, I guess. I'm coming to realize that there are growing numbers in both IS camps: One swears by it, and the other believes it to be almost gimmicky.