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> It does improve performance, but doesn't magically turn it into a ASM/C/C++ executable for the reasons set out above.

Isn't that, however, exactly what the Mono folks are doing with MonoTouch to get apps written in C# run on iOS (and approved in the App Store)?

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Not really - they're just swapping out the libraries for ones that they can use on iOS. It's not going to be portable off of iOS, etc. (EDIT: That is, the iOS specific UI code - obviously non-platform specific library based code will be completely portable)

Plus it won't be as fast as writing it in C/obj C as it will have garbage collection overhead, type checking, bounds checking, etc etc. (For iOS style UI apps this isn't a concern as they're mostly just thick clients to real calculations done elsewhere, so speed barely matters as you are just relying on the speed of UIKit for graphics anyway.)

Yup, thats exactly what Monotouch does. It's something like:

C# -> IL -> Mono AOT* -> ARM binary -> xcode/LLVM -> normal iOS binary

* AOT = ahead of time compiler - like JIT, but... before it's needed. There is a linker step in there to remove a load of stuff too.

Works _great_.

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