You cannot move users  with a Backup and Restore.

heres a simple rule:

use smigrate if you dont care about users  or permissions and just want data, or need to move a WSS subsite to another place.
use stsadm if you want to create an IMAGE of the site  - retaining EVERYTHING (except of course wppacks that are custom that the site uses)


the ONLY caveat to using stsadm is that you cannot backup  a "subsite" of a WSS site - for that you have to use smigrate.

I don't think even stsadm will move USERS. Users are managed in Active
Directory not SharePoint.

yes thats true - and stsadm can only be used on the same domain if moving  servers.

A Little off the topic but.... try using AvePoint's DocAve. It moves things seamlessly all over the place and keeps all of your permissions and cross site  groups. I use it to move my companies site's from Dev into our Production farms