Now the word is spread, so I can blog that as well: Windows Server 2003 SP1 (and the x64 Version) will finally introduce the feature that folders underneath a share can be hidden when the user browsing the parent folder or share has no read-permissions on that folder. It's been requested for years, and finally made it's way to Windows Server. This feature is called Access-based Enumeration.
You can switch this on and off for every share with a commandline-tool (abetool.exe) and in the final version this is supposed to be supported by the GUI as well.
Joe Richards, MVP for Windows Server - Directory Services and author of the Joeware-Tools
has created a the tool ShrFlgs
which also enables the Access-based Enumeration on Shares.