I use the lens since the end of August on a D800 and now a D810. I was very skeptical Tamron was me more of a concept than Low Budget supplier and I am [unfortunately] a perfectionist. But ultimately, I'm not a millionaire and have also no Lens Boy of my quality, sauschwere and expensive alternatives carries afterwards. The lens has perplexed me utterly. It's amazing how good the picture quality, thanks to the minimum focusing distance even succeed macros by cropping. I had never "muddy" images as reported here, which I think a camera error in other respects. By fehlfokus or incorrect exposure The focus is seated and is fast. The exposure I have to correct the camera kindly by one stop down, so an f-stop faster. The VR is enormously well succeed sharp images with 1/150 from his hand at 600mm.
Conclusion: simply unbeatable at this price.
I have a few image examples, some with extreme backlight from the front at 600mm!