Don't be deceived by the ad pictures. This thing is huge! Have to first get used to the size and weight!
Did not get a chance yet to play with it in full swing. A 'snapshot' that I took with it is in the 'Photo Theme/Sky Theme' thread.
Cheers!
And by the way, its only a 100 or so $ difference between the 15-30 and the 12-24
I just bought the Tamron Af 17-35 f2.8-4 Di LD Aspherical, but it hasn't arrived yet. I read many reviews and it seemed to perform better than it's Sigma counterpart, and was supposedly "on par" with the Nikon 17-35mm.