Just got the new Tamron SP AF 70-300mm LD Di VC, and I've got to say, this is the first time I've had a "Wow!" moment with my Nikon D300 body. I had the chance to shoot some models in Texas last month (November 2010) and all I can say is, "What is Tamron thinking selling this lens for as little as they do? Every review says that the image stabilization is like "magic" but until you try it, I guarantee you've never seen anything like it before. One caveat, it does not work as well for slower speed panning as you might think. There's a good reason why (I suspect). When the camera body refocuses, as it does in Continual AF mode, the VC system attempts to "recenter" on the new point. If you're using just one AF point, it's not too bad, and the image only jumps occasionally in the viewfinder. But, if you, like many people, like using the 51, 21, or 9 point AF modes, the action of the VC becomes a bit helter-skelter. Often, it jumps right as the shutter is released, causing just a little bit of unnecessary blur in the resulting image. I found the best panned images came from turning off the VC, at the 1/125 and 1/160th second shutter speeds I was using as a test. It badly needs a panning mode switch.
With that said, however, it is pure magic for kids, people, pets, and anything much slower moving. Image sharpness and contrast is excellent, even wide open, on the Nikon D300 APS-C sensor. Don't look at this as an expensive consumer-grade zoom lens. Consider it a very sharp, image-stabilized 70-200mm f4.5 lens with the added benefit of another 100mm of focal length. A viable alternative to Canon's 70-200mm f4 "L" IS lens which has just come out, but at less than half the street cost. THAT is money you can take to the bank!
I'll have some photos to share, posted in a little bit.