Compilers are great at some things and really bad at other things. The C and Fortran ABIs are too permissive in some cases, making certain optimizations impossible for the compiler to do (without combinatorial growth in generated code size). On x86-64, you can go a long way using SSE intrinsics, but that is pretty close to the assembly level. IBM did a bad job designing the PowerPC intrinsics, so they are nearly useless. There are a few computational kernels that I have sped up by a factor of two relative to what the compiler could produce or the best published result. The x264 project writes a huge amount of assembly and provides consistently better performance than other implementations. There is still a place for assembly, although it should be kept localized.