Actually, one caveat is that GCC's optimization info can be rather inscrutable because it's in terms of compiler internal nomenclature. That's a definite area for improvement (or compiling some sort of key to it).

Indeed, GCC optimizes well. Last time I ran a set of Fortran benchmarks, the geometric mean for them was competitive with other compilers on multiple architectures, and some of the benchmarks could have been sped up considerably with specific compiler options or by re-writing a function sacrificing numerical equivalence, which the Intel compiler seemed to do itself.