Authenticaion Choices

[Chiu, PCM (Peter)]

Hi there,

Not sure if this is the right forum to pose some questions about
authentication.
Please redirect me if not.

I would like to know what people's views are regarding 
the use of LDAP or/and Active Directory for authentication
on a group of (160) mostly Linux based servers mixed with a handful
of XP machines.  

In particular, I would like to know
a. how reliable these servers are on Linux,
b. how flexible to allow new clients to be added,
c. how easy for users to change their passwords and get populated
across, and 
d. if it allows file sharing over NFS or samba.

Many thanks for any pointers in advance.

Peter