Is the Nikon 105mm f/2.8G AF-S VR Micro Nikkor Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 105mm f/8.0 test image. Observe the contrast and resolution of these results.
Is the Nikon 105mm f/2.8G AF-S VR Micro Nikkor Lens set to 105mm f/8.0 sharper than the Tamron SP AF 90mm f/2.8 Di Macro Lens set to 90mm f/3.2? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.