This would be used by KDE 4.3.4 by USE="lzma" in kdelibs, ark, and kdebase-kioslaves. ~arch version of libarchive and eix have forced this over lzma-utils since the beginning, so it should be fairly well tested as most users use at least eix
amd64 stable
ppc64 stable
I've been using xz fine since mid-October on x86.
Stable for HPPA.
x86 stable
arm stable
ppc stable
alpha/ia64/sh/sparc stable
closing, both m68k/s390 is stable: xz-utils-4.999.9_beta.ebuild: KEYWORDS="alpha amd64 arm hppa ia64 m68k ~mips ppc ppc64 s390 sh sparc x86 ~sparc-fbsd ~x86-fbsd"