I think it's a cardinal sin for Cappuccino to replace native scrollbars and native scrolling. Maybe your UI gets to look a teeny bit more unified, but scrolling is almost as primitive an interaction as mousing. It is carefully tuned on every operating system and changing its behavior for one part of my screen always sets off my nerves. This non-native feeling is the sort of thing that Flash usually gets flak for.
Would you use a website if it messed with your mousing speed or your cursor? You would you grind your teeth. I feel similarly about non-native scrolling.
The only exception I will grant is for people developing fling scrolling for webapps on the iPhone and iPad, because that is carefully tuned to mimic one operating system on one kind of device. Anything for more general web browsers, however, can make no assumptions and should leave my scrolling alone.
I've already read it. The scrollbar itself is pretty, but you cannot exactly capture the precision of a mousewheel or in my case, a two-finger scroll event. For me, the two-finger scroll speed is disturbingly faster than other windows that scroll, which makes navigating Cappuccino apps unnatural compared to normal pages. For the git issue browser, where long lists and comment threads are everywhere, it distracts from my ability to use the app.
You won't be able emulate scrolling fully until there is a standard for mousewheel events that includes full X/Y delta information instead of uniform discrete steps. I haven't seen any plans for this in HTML5 or elsewhere. And at the end of the day, anything done via JavaScript events is just not going to match the reponsiveness of the browser scrolling the element natively; for such a fundamental operation, the cosmetic benefit of a reskinned scrollbar just does not outweigh the UI friction.
