Actually ldap would be using NIS (which LUM also does.....), but instead of using NIS (ie. unix nis) it would be using any ldap backend where users are posixUsers (or inetOrgPerson really depending on the schema).
I've just asked for this feature, but in general if one look at a normal Linux box there is a way to use a ldap backend for authentication and authorization. Authentication is the username/password part, the authorization is the more interesting part as this is where the uidNumber and gidNumber is provided (getent passwd, id, etc, etc).
Now that one have pointed in the Novell direction, it would be possible to create users using Novell IDM (lots of options there), but for a home user that would be "overkill".
I would just like to have the normal LDAP intergration found in normal Linux distributions, which only allow for testing on a single group, and a search filter - but people asking for this would know how to deal with that before going in that direction in the first place.
The main issue, is that if one have more than a couple of computers (Linux/OSX) using NFS things will get complicated due to the different ways the distribution assign uidNumbers.
Being able to "modify" uidNumbers/gidNumbers manually would be a step in the right direction, but it's not going to solve the whole situation.
btw. LDAP is not an addressbook, it can be used as, but it's more than that.