This has been a real headache for me:
s2ram was broken for me with newer versions and I spent hours to find out the reason.
Today I found that CONFIG_FB_UVESA must not be set in the kernel to make it work
So I think it would be very helpful to have something like this in the ebuild
if linux_config_exists; then
linux_chkconfig_present FB_UVESA && die "FB_UVESA must not be set in the kernel"