I also have an S3IS and I looove it. I don't get many blurry pics with it, but one thing I *do* notice is that if the lighting isn't just right, it has a hissy fit and my pics are grainy and gross, lol. But I think that has more to do with me than the camera, lol.
Julie - I took mine to Disney and my pics turned out awesome compared to my MIL's pics with a smaller Canon. I just put it on "action" and snapped away. There were a small handful out of 500 photos that didn't turn out - compared to nearly half of her 800 photos. She got some awesome shots that I didn't, but mostly because I didn't think to have my camera out for some of the pics, lol.