I own this lens, and am not impressed. the CA is quite strong in almost al instances ( see the 2nd pic in this thread) and there is not enough detail left in any shots to crop. @300mm you have to stop down to f/6.3 or 7.1 to get a decently sharp image. the colors are not all that vibrant either. The USD and VC do work decent. I recently bought a used 70-200 f/4L for $350 that MUCH outperformed the tamron in distant detail, even though it was lacking 100mm. at 200mm f/4 the canon outperformed the tamron hands-down, even at f/6.3. (tripod, iso 100, broad daylight). unfortunately the aperture motor was defective and didn't always close down, and I had to return the L. I now have the 70-200 f/4L IS on the way, and will most definitely be selling the tamron.