I shoot only still images but I've gradually moved all of my lenses to IS. Currently, my three principal lenses are the 100-400 f4-5.6L IS, the 70-200 f4L IS, and the 24-105 f4 L IS. I do a lot of wildlife shooting and at low light and slow shutter speeds IS is a godsend. Even then it's not perfect. With my 100-400, anything shot handheld below 1/200 of a second is noticeably soft. I can get slower shutter speeds out of the 70-200 and the 24-105 due, most likely, to their considerably lighter weight, but with these lenses below 1/100 is problematic.