Are You Really Seeing Your Sharpening?
When you apply sharpening to your image using the Unsharp Mask filter (under Filter, choose Sharpen), make certain that when you apply it, you're viewing the image at 100% size. Most other views won't give you an accurate view of how the sharpening is really affecting the image. To make sure you're viewing at 100%, just double-click the Zoom tool in the Toolbox.