Quote Originally Posted by btaylor
will leavingIS on while shooting at high shutter speeds actually be detrimental to the shot?

In addition to the battery drain, it can cause its own blur if you happen to take the picture while the I.S. lens group is moving.


Quote Originally Posted by btaylor
At what point (shutter speed) does IS become useless?

I turn it off for anything above 1/500.





"Because it tends to be counterproductive above 1/500. Everyone seems
to think that VR has an infinite cycling time. It doesn't. It's
sampling frequency is just above 1/500. Most pros turn it off for
sports. "


http://www.bythom.com/discipline.htm



"VR off. In fast action, there is no time for the VR to settle, and
it will still be "VRing" while you're taking the picture. Fighting you,
rather than helping you. "
http://forums.dpreview.com/forums/read.asp?forum=1034&message=31828838