Is the Tamron 17-35mm f/2.8-4 Di OSD Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 24mm f/16.0 test image. Observe the contrast and resolution of these results.
Is the Tamron 17-35mm f/2.8-4 Di OSD Lens set to 24mm f/16.0 sharper than the Nikon 16-35mm f/4G AF-S VR Nikkor Lens set to 24mm f/4.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.