well yeah, if you use an icon-editor you will often find that icons have VARIOUS sizes, but once you try to expand any icon past it's largest (supplied) resolution/size you get the same effect as resizing upwards an image, you WILL get pixel-blur. One way to improve this, as you've done, is to download hi-res icons from somewhere like http://www.iconfinder.com/ (I use the png icons, they're much sharper)