Great look for the money, although the lens is shaking inside!

Do Not Worry. I, too, was initially more than worried because the lens wobbles especially when turned off inside as if a lens or the OS would be defective. The mentioned on Amazon, no reviewer. In various Internet forums but I have already read that this is normal, because the lens is clamped electromechanically only when switched on. Sounds strange, but is the official representation of Sigma Germany. Will already be so, but that should also write in the same Sigma in the manual before the unsuspecting buyer is on the verge of a heart attack. I got the lens and tested today after a working day on my EOS 7D in the semi-darkness of my apartment. So hats off, the light intensity is impressive, the colors very well and the autofocus absolutely fail. But that is certainly at unbeatable autofocus system in the EOS 7D. Anyway, after the initial shock, I'm excited and I'll get back when I tested the 17-50mm sufficient even in bright light and also on my EOS 60D. Selling my KIT lens (18-55mm with STM engine and built in 2014) of Canon I regret anyway not.The Sigma 17-50mm, f2.8 makes a much better impression, although it is only twice the aforementioned KIT lens cost.