For me, just maybe. I'm going to at least give this a solid look.
We have a loose migration plan for all of our x64-based Microsoft Windows servers to IBM Power Systems. All except our Active Directory servers. We use those for Group Policy, Domain authentication, Domino web authentication, DNS and a few other familiar functions.
As per ZDNet, the release of Samba 4 appears to be a viable alternative to Active Directory. More to come once I dig a bit more information about it. I wonder if I can run it on IBM i? :)