Image Stabilization (IS) was introduced in the 1st Canon lens in 1995 I believe, so before the 1st Canon 1DS body (DSLR).
As I understand it, the vibration the IS is "looking for" is the type that comes from handholding, hand shake, body instability. It has a cadence and frequency to it that is longer than a high shutter speed exposure. So the IS is ineffective at very high shutter speeds but can still motion effectively at slower speeds. The Canon 100-400 gave me a ton of stability when I had it (better than the Sony I use now). It's also general knowledge to turn IS off if the camera is on a tripod, but I constantly forget to do that with my Sony cameras and see no impact. The Canon Lens Work III says that this was resolved early on. High ISO comes at a price of course, so with IS I prefer to knock my ISO down a few stops if I'm not using a tripod and have IS to help.
As for "needed" vs "nice to have" it is surely dependent on the photographer. eg a street photographer with shaky hands, slow lenses, dull days etc will see a significant advantage. A land/sea/citiscape photographer who always uses a tripod will have little or no use for it. Plenty of grey between those examples of course.