I'm a great fan of NIS+. Not only is it very easy to set up and use, it scales well and it's dead easy to manage the data stored in it.
(Much easier than old NIS or LDAP. Sun could be suicidal and ditch it, as they've been threatening too, but replacing it with dramatically inferior solutions like NIS or LDAP is going to make a lot of people miserable.)
Of course, it doesn't always work perfectly. I just had this one case where it stopped working. The server partially booted - the NISplus server was running and serving clients. It's just that the NISplus client on the server wasn't working. So lots of other things wouldn't work. Amongst others, the NFS server. So while I could log in to a client, I couldn't access any files. Bad!
(Some testing indicates an RPC authentication problem. But basically everything goes into the RPC black box and never comes back.)
The only thing I had done was to change the IP address of the server. And yes, I had run nisupdkeys -a to update the server's addresses. So my theory is that somewhere buried deep in the bowels of NISplus is some memory of the machine's old IP address, and I can't spot it right now.
(I managed to get it working again, but I'm not sure which of the half a dozen random kludges was the one that mattered.)