Opinion: Best form of SR for telephoto shooting.

Question: I've heard from many people that turning of IS on tripod shots is better, and it seems I have experienced that result too. Is there ever a time when hand held shooting (certain shutter speeds) that it is better to turn it off, or will I ALWAYS get better results with it on? In other words, If I have enough light to shoot at 1/8000 for example, should I turn off IS during handheld or will it still help even with that high of shutter?