OpenBSD still supports it. It's very stable too.
It supports cool stuff like acting as an ldom host too. http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man8/...
Huh, and here I was figuring that switching Solaris to OpenBSD on my SPARC hardware would mean not getting to tinker with logical domains anymore. I'm glad to see that my assumptions are incorrect, and that my Sun Fire T2000 will have an actual reason to be running in all its loud, jet-engine-sounding glory :)