There have been a few threads about this, so while I was doing a tripod/OIS test, I decided to do a snapshot OIS and high shutter speed test, to illustrate why I leave it off if I'm in good light. You can get worse or better results than this, depending on your background and when you "catch" the image stabilization system doing its job. I see a difference, so I leave OIS off unless I need it. But, I try to turn on a light, or use stabilization first. Photos taken handheld. Cropped and "auto tone" adjusted in Lightroom. First photo is with OIS off; 2nd photo has it turned on.