It's unfortunate that PowerShell doesn't come with a built-in "Get-ADSIObject" cmdlet. Undoubtedly a similar cmdlet will be available in the future, but it is not yet included in PowerShell v1.0. You can use WMI to perform some ADSI queries. You can also use the underlying .NET Framework directory services classes to manipulate AD. However, using those classes moves beyond the realm of scripting and pretty firmly into the world of .NET Framework programming.
Review Chapter 12 for some examples of what you can do in PowerShell regarding ADSI. For now, continue using VBScript for more complex ADSI-related tasks.