10 out of 10 points and recommendedSharp-sharp center, great for low light, portrait lens
I moved from a Pentax system to a Nikon system recently and was looking for a "normal" lens for my new D300. I wanted a fast, low light lens and was introduced to this lens.reviewed December 4th, 2008 (purchased for $450)
At first I was skeptical. On a couple lens review sites, this lens didn't score extremely high for some reason. After examining the test data, I understand that it is because the corners are soft until the lens is stopped down a bit. I am more interested in center sharpness. This lens is extremely sharp in the center area. I would say that it out-resolves the D300 sensor in the center. It really doesn't get soft until you get about 3/4 of the way to the corners. And even then, if you stop down to f8 - is is sharp from corner to corner.
I have read some negative reviews about this lens from some folks that must not know much about depth of field (DOF). With this lens, the DOF is shallow of course! Especially close up to your subject. If you think an f/1.4 lens has shallow DOF, try an f/1.2 lens!
Anyway, it is a remarkable lens and I highly recommend it. I am a pixel peeper, and I like it. So I am sure that most everyone will like it too - providing you understand how to shoot with a fast, shallow DOF lens.
Compare the SLR Gear evaluations of this lens and the Carl Zeiss 28/2! The highly rated Zeiss 28 is about $1200US, while the Sigma is about 1/3 the price! And the Sigma is auto-focus, while the Zeiss is manual focus.
Edit: After reading some posts that gave a 2 or 3, I had to raise my rating from a 9 to a 10. These folks really shouldn't be rating lenses if they don't understand how to use them properly. (Not the posts that had defective lenses.)