Historically, it has been my experience that pretty much all the non-x86 platforms the compiler and hardware specific optimizations tend to have a pretty dramatic impact. Intel just has so much code and existing code streams to factor in to their designs for new hardware. Maybe this has changed. It's a hard road if mismatched or non-hardware optimized binaries are slow and pokey and hardware specific optimized binaries are competitive. Come out with a great 64bit ARM core that can run nearly all ARM binaries with decent performance (clearly, excluding stuff that needs custom hardware..) and ARM could be pretty disruptive.