According to Don Jones, author of the TechNet Magazine Windows PowerShell column, File Permissions are one of the most common requests. Unfortunately, permissions in Windows is a complicated matter and there is little Windows PowerShell can do to fix this innate complexity. However, Windows PowerShell does offer some valuable features, such as the Get-ACL and Set-ACL cmdlets, that do offer a powerful way to work with Windows permissions.
In the February issue of TechNet Magazine, Don outlines how permissions work in Windows. He then explains how you can use these cmdlets to work with permissions. But, more importantly, he takes a look at how you can incorporate familiar command-line tools (such as Dsacls.exe, Cacls.exe, and Xcacls.exe) to further simplify the task at hand.
By the way, did you know that the Windows PowerShell 2.0 CTP is now available? Check it out and see what's new in the latest version.