I bought a used copy of this piece to use in my nikon D90. The lens is 3 years old and it is perfect, no problems due age, except to the rubber focus ring that is a little "dry". No front or back focus.
English is not my mother language, I will try to be "understandable"
Well, first of all is a big, heavy and bulky leans and it uses a big filter. People get intimidated by that lens, its nice!
About IQ I can tell you I like when used at day, despite being a f 2.8. Its a little soft at wide open and you need to step down a little bit. Center shows a very high quality image and borders are a little soft. I found some distortion CA and purple fringe wich is 100% correctable (at least with the lens profile in Lightroom 3). So, if you are shooting landscape, or buildings at wide open, I can tell you, with the correct exposure, you have a very high picture quality. I can tell also, in this scenario, it perform better than D90 18-105mm lens kit. It produces a warmer tone than 18-105mm lens, I love it, and 90% of shots I do only need to apply lens profile, because image is very well balanced (colors and the exposure) already. This is the kind of lens that dont give work to you on the post processing. AF works great and it is not as noisy like people complain. To be honest it produce less noise than my nikkor 50mm 1.8D.
But, here comes the bad part.
I am disapointed by lens performance at night. When you shoot, the darken part of the image get blurry, like a out of focus blurry noisy image. In this case, the darken area of the image have a very poor quality and it is not sharp. I know you are thinking "that´s is normal, it is the dark problem", but it is not. I can tell that because the 18-105 kit lens, in same scenario, perform 200% better, and even with the noise, the image is focused in dark area, not blurry or out of focus..... I found this problem in every aperture range. In other hand, noise in dark area is better than the 18-105mm, because somehow does not show purple dots, only black ones.
The bottom of line is, it is a very good lens for the price charged and the performance to shoot landscapes or portraits with the correct exposure, aperture and with the right ammount of light, do a high quality sharp image. It captures a very good skin tone also.
The zoom ring is not smooth in all range, maybe because the front element is heavy.
If you have a nikon and want to have a lens that suit FX and DX sensor and you want to save some cash this is the lens for you.
A sample of this image quality:
Here you can see more samples about its image quality:
http://www.carloshackmannphotography.co ... 6042_84Boe
http://www.carloshackmannphotography.co ... 6803_2KmZS
http://www.carloshackmannphotography.co ... 5287_X9YfT
http://www.carloshackmannphotography.co ... 4258_DgMni
http://www.carloshackmannphotography.co ... 2720_8Qc8s
http://www.carloshackmannphotography.co ... 3477_iHANk
In my opinion:
Cheap, high performance with correct exposure, aperture and ammount of light
Bad performance at night