I dislike non-standard controls. We sometimes run into them because the application is cross-platform, and the developers are either too lazy to bother giving the controls a native UI, or their cross-platform tool prevents them from doing so. That’s why I’ve never even downloaded an Adobe Air application. Yuck.
Other times, the developer gets creative with the look of the controls, but in doing so, rarely adds enough value to make up for robbing users of their familiarity with the native look-and-feel.
One exception is the scroll bar in Tweetie, a Twitter client:
It is simple, with an ever so slight gradient. But the best part about it is the utter lack of background. If the information fits entirely in the window, the scroll bar disappears entirely. Beautiful.