Thanks for confirming this, mdm; that's what I'm also forced to conclude unfortunately. Explains why I'm not getting sharp results handheld in the upper ranges at only 1/500, thinking all the time that OIS was giving me a buffer zone. Oh, well, In this case will need to keep the shutter above 1/1000 (1/2000-4000 even better) and hike the ISO for the long shots. Dammit. Bought this lens on the road in Mexico (Amazon Mexico) and it'll be some months before I'm back and can send it in for service (that is, if the warranty for something bought here even holds in the US). With no previous experience with OIS, I didn't detect it soon enough, while I still had the box, packing, and an oportunity to return it to the vendor. Oh, well. Kinda disappointed here, as I had to pay top dollar for this puppy. Love it otherwise for street, as it's become my most productive lens in this environment (even though I expected to use it only for occasional landscapes). So OIS is important; it's tough getting sharp images handheld at 150-200 no matter how steady I am. Hell, back in the day, I wouldn't have dreamed of walking around shooting handheld with a lens that is effectively 300mm full-frame at its upper limit, so was counting on the stabilization feature. No opportunity to try it on another body for the moment, but I kinda suspect that's not the problem; it's probably just the switch.