We have a new iMac on Snow Leopard authenticating against an OpenLDAP directory. Homes are on (automounted) NFSv3 (Linux, kernel-server).
NFS seems to work pretty well (if a bit slow, but we don't want to risk not using locking).
When a user logs in using an LDAP account, however, weird things happen: Sometimes the machine hangs even before all the Desktop icons had been initialized, sometimes the user can work for a little while, but after a while the machine starts hanging: New processes by the user don't get off the ground, old processes cannot be quit (even force quit hangs). Sometimes early on, sometimes later, the dock doesn't react at all (does not show context menu for programmes) and the Finder won't take focus.
All the same, even if everything else seems to hang, I can log in via SSH and at least cleanly reboot the machine. SSH login works even for LDAP users. If I disable LDAP, everything seems to work normal for local users.
We used the OpenLDAP directory with RFC 2307 mapping. We only really use it for account data, so I tried removing any mappings except the Person, User and Group mappings in the Directory Utility. Both mappings have the same resulting misbehaviour.