Is the Canon EF-S 15-85mm f/3.5-5.6 IS USM Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 15mm f/3.5 test image. Observe the contrast and resolution of these results.
Is the Canon EF-S 15-85mm f/3.5-5.6 IS USM Lens set to 15mm f/3.5 sharper than the Nikon 16-85mm f/3.5-5.6G AF-S VR DX Nikkor Lens set to 16mm f/3.5? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.