Symbian: Linux unfit for mobile phones (the Register)

The Symbian consortum managed to splinter SymbianOS into incompatible platforms all by itself, which has only been corrected by Nokia finally buying out its remaining partners. And the use of C++ classes in the OS API practically guarantees that they will break binary compatibility again.

As for resource-efficiency - SymbianOS was highly optimised for its platform, but that was a Psion PDA with a few megs of battery-backed RAM storage, not a mobile phone with hundreds of megs of flash storage. You can't execute-in-place from cheap flash storage, which made it very slow to start programs and to boot, though I understand it does now implement demand paging.