Hi Thomas,
Since you mention quota trees, I'd like to jump in and discuss the benefits of quota trees within 5.1 (shipping soon) and backup:
My recommendation is that you should arrange your data in quota trees whenever possible when running 5.1 for these reasons:
1. You can have different security models running on a per quota tree basis (ntfs, mixed (multi-protocol) or unix).
2. Pass I & II of dump has been optimized for full quota tree (as well as full volume) backups.
3. dump has a new Q option that allows all non-quota tree data to be backed up. This allows you to frequently backup quota trees, but perhaps backup /etc and other miscellaneous data on an infrequent basis and you don't need to backup the whole volume to do so.
Cheers, Grant