With KMS enabled, the gentoo-2.6.34-r1 kernel crashes X on radeon GPUs. See the URL for a detailed error description. The important part: gentoo-sources-2.6.34-r2 has the fix (see drivers/gpu/drm/radeon/radeon_agp.c:270), while 2.6.34-r1 does not. So i'd prefer the -r2 over the -r1 to be stable. Reproducible: Always
Thanks, eventually a subsequent stable release will include this fix.