Yesterday, I got a question about using the FAI nfsroot for a diskless client setup. I knew, this should be possible, since the FAI nfsroot is used for diskless client booting. So, I just tried it myself. It'v really very, very easy! Here's how I've done that:
http://wiki.fai-project.org/wiki/Use_nfsroot_for_diskless_clients -- regards Thomas