As per topic, x11-libs/gtk+-3.20.9 has gone stable on a number of arches, causing current stable versions of greybird to royally mess up rendering. Please stabilize x11-themes/greybird-3.20.1-r1 or newer as soon as possible to address this.
I ran into an error compiling this greybird, I think because my current ruby profile (ruby23) doesn't have a corresponding rubygems built for it for some reason.
Stabilized amd64 with a nod from perfinion. x86 AT please stabilize (this package should be fine but I don't know what the status is of dependencies on x86) @rnddim - your compilation error would seem to be something related to ruby for sure; as long as sass is installed properly it should just work -- i've received confirmation that it's fine from other people in #gentoo-dev for ruby23.
x86 stable