[Samba] When do I need idmap mappings?

[Gémes Géza]

Hi all,

Sorry for this stupid question, but what are the newly introduced idmap 
mappings good for?
1. When I want to use security=domain, or security=ads and automaticaly 
create UNIX users on the fly through winbind, and avoid 2.2.x's winbind 
uid range problems (the same user mapped to a diferent UNIX users 
between sessions)
2. NT4 Domain trust ??????
3. ?????

So I'm about to play arround with 3.0beta3, but I'm not sure if I need 
idmaps or not.

Any help would be apreciated.
Thnx in advance.

Geza Gemes