I've just tried this today, and haven't yet got it to work. SME7 without the _very_ latest updates. XP pro SP2 on the client.
I created a group called "powerusers" and made the description "Domain Admins", then added a couple of users, then did a post-upgrade (incase templates where involved), then re-booted, then (domain) logged in as one of the users. and used my standard test to see if it would allow me to change the system time by double clicking the time in the system tray - it wouldn't.
I looked in various templates and /etc/smb.conf, but couldn't find any entries.
Anyone know if/how it works?