results have been added to the Tamron 15-30mm f/2.8 Di VC USD Lens review
I think that you are going to like what you see from this lens. You will notice strong barrel distortion at 15mm (details in the top crop sample get enlarged) and some chromatic aberration to be corrected, but overall this lens is looking good including at f/2.8.
Here are some comparisons: Tamron 15-30mm VC vs. Canon 16-35mm f/2.8 L IITamron 15-30mm VC vs. Canon 16-35mm f/4 L ISTamron 15-30mm VC vs. Tokina 16-35mm f/2.8Tamron 15-30mm VC vs. Zeiss 15mm f/2.8 B&H
has the Tamron 15-30mm f/2.8 Di VC USD Lens
available for preorder.