Lightning Fast autofocus

The Sigma APO DG OS HSM 150-500 5.0-6.3 lens I now have a few months to my Nikon D200 in use. It makes a very sophisticated look, clean finish. It was supplied with a lens hood, a quiver, a tripod mount and a carrying strap, the warranty is 3 years.
I have the lens on a monopod mostly in use, but sometimes I also take pictures freehand if I want to capture quickly as birds in flight. The HSM engine is extremely quiet and almost almost inaudibly. With only the image stabilizer has a good chance of being able to make a tidy sharp photo. Are in the telephoto range up to 450mm, the photos usually very sharp. Fully extended with 500mm telephoto, I feel that the sharpness softens a bit, but that's perhaps only a subjective impression. One can long telephoto in his free hand, because of its weight and the length hardly keep quiet right. I attach the long "bag" then like somewhere in, camera bag, heruntergekurbeltes car windows, fence etc. In such immobilization should turn off the image stabilization better. Chromatic aberrations or other aberrations I have not found.
The autofocus is very fast, I was surprised by this quality. The weight is 1.9 KG not entirely without - and the length of the lens does not. I have therefore specially bought a particularly large and stable photo backpack that I can rebuild with a rack for trolley and strutting behind me.
Overall I am very satisfied with the purchase and can really recommend this part.