I spent an inordinate amount of time fighting webkit before switching all of our stuff to native. The four biggest problems, I think, with the state of webkit are: 1) Implicit memory management of large images/surfaces isn't reliable. There's basically nothing you can do (outside of not doing anything) to prevent your page from crashing webkit if you use too many (where too many is undefined) accelerated elements/tot…
I'm not a mobile webdev, but about (2), did you try using Webworkers for the background tasks? iOS Safari supports it nowadays, right?
Yeah, but they must be in a separate file, among other things. They're really not feasible for lightweight dispatch like GCD is.