As long as it merely "skins" the toolbar and doesn't try to override the browser scrolling function, like this terrible, terrible WordPress iPad theme which scrolls through javascript, making it ridiculously jerky and just weird... We're already "skinning" input elements with CSS which by default would look native to the OS, so that makes sense.<p>The web has grown up since IE5 (where you could merely <i>color</i> the scrollbar) and graphic designers will design some proper ones fitting with the whole site design, while a bad scrollbar design will just be an element of an equally bad site otherwise.