Offline caching does work in iOS4.2/4.3
I'm the technical lead for a fairly substantial iOS-targeted web app that has a major offline component. And I can state the offline app caching via the HTML5 manifest does work.
There are issues with caching that can lead to frustrations and outright failures (the implementation is very sensitive to errors in the manifest file format and the user/UI feedback and API for controlling cache leaves a lot to be desired). But we are running this app offline as needed.
Regarding performance: We have not yet benchmarked our app running under Web.app (the home screen Web app runner) vs. Safari.app on 4.3 yet. The app is do quite a bit work charting mid-sized data sets, so speed matters.
Biting the hand that feeds IT
