This should a warning to all over-enthusiastic designers/developers on the Internet. Please stop creating custom scrollbars. Web browsers already provide wonderful scrollbars.
... for the sake of preserving the status quo of default scrollbars, no less?
Come on.
The idea might be good -- most people are right-handed and might have better response times with their right leg when it's straighter. But there's too much inertia in the current convention, and the change can't be made incrementally without creating serious risks.