Image quality test results have been added to the Tamron 18-400mm f/3.5-6.3 Di II VC HLD Lens page.
Clear is that this is the longest focal length range available in a DSLR lens. Is this the first superzoom to break the image quality barrier? That answer is not so "clear".
The Tamron 18-400mm f/3.5-6.3 Di II VC HLD Lens is in stock at B&H | Amazon | Adorama.