Thoughts on SIGMA 24-70mm lens?

Thinking of buying 24-70mm sigma lens for Nikon D3100.
Do you own it? How's the quality and would you suggest it for my camera since is a crop sensor camera?
Is it suitable for candid, street and a little all around photos?

I don't own a 24-70mm but I do own a 12-20mm sigma and the quality is outstanding. I use it mainly for my landscape ocean shots. I used it on my D3100 as well and its great. I highly suggest Sigma. People who talk down about it or only say to buy Nikkor is pathetic.

Please check this out too, this is a discussion about the sigma 24-70 you want.