Is the Tamron 18-200mm f/3.5-6.3 XR Di II LD Macro Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 200mm f/7.1 test image. Observe the contrast and resolution of these results.
Is the Tamron 18-200mm f/3.5-6.3 XR Di II LD Macro Lens set to 200mm f/7.1 sharper than the Nikon 70-300mm f/4.5-5.6G AF-S VR Nikkor Lens set to 200mm f/5.3? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.