Is the Tamron 70-300mm f/4-5.6 SP Di VC USD Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 300mm f/5.6 test image. Observe the contrast and resolution of these results.
Is the Tamron 70-300mm f/4-5.6 SP Di VC USD Lens set to 300mm f/5.6 sharper than the Canon EF 70-300mm f/4-5.6L IS USM Lens set to 200mm f/5.6? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.