Hello dewets! Yes I agree with you about low CPUs but I don't think that is the main reason.
I tried iScroll on a iPhone 3G and it was smooth enough to make me think about a native app.
I'd rather think that the "overflowed-div" is not optimized enough natively in the browser code (the real iframe is not implemented at all). And jQM need to be optimized a bit more.
Maybe coding native JS inside the jQM code should help a bit.
I submitted my POC to the jQM guys, they were already working on it. So a better code than mine would probably be included in the next release.
=> 2) Proper fixed headers and footers
Yes, for instance it is lacking of this functionality, but I believe that as soon as the real scroll divs are implemented, headers and footer will be nicely fixed and won't disappear/reappear like it does right now.