Hmmm fairly interesting benchmarks - but a bit predicable in the outcomes... Although I had heard that Os only took a 10% hit...
I was hoping that you would have tested more esoteric stuff like the so called "Graphite" optimisations ( -floop-interchange -ftree-loop-distribution -floop-strip-mine -floop-block ). Have always been too scared to try these on any applications on my Gentoo install (they are commented out in make.conf)
I have used the lto (delayed link time optimisations) with gcc 4.7.1/2 - while I have a list of stuff that falls back to no-lto, it's not unmanageable. Naturally doesn't appear to make much difference with day-to-day usage