I have an iPad. When I push up on a webpage it scrolls. Which part sucks?
The whole page can scroll (on iOS 4), but not individual parts of the page. That's what he's been trying to address, and that's the hard part.
And you can't have a fixed-position footer while you scroll around - loads of problems there, not the least of which is that you don't get JS events until the scroll is finished. The only way around it that I'm aware of is to fake all the movement in a fixed-space page, as done here.
MobileSafari in iOS 5 supports momentum scrolling for scrollable individual parts of the page, here is a blog post about it: