Been on Gentoo for a long time. My current image has been rolling forward since 2008 which is when I switched to 64 bit but I started using it long before that.
I value transparency, control and customizability. I occasionally look into other options (and use them at work and in other contexts) but haven't yet found a better fit for my personal preferences.
I actually have my CFLAGS set very conservatively. Stability is more important to me than squeezing out that extra juice and I like to be able to switch to a different CPU family without too much work. My desktop is sort of a Ship of Theseus, everything has been replaced several times over the years and it has gone back and forth between AMD and Intel more than once.