Windows Server 2008 mapped drives not showing on workstations?

Group Policy Preferences work great on Vista and newer OS. If your environment is all Vista or newer, use Preferences. It's straight forward, easy, and works. Preferences will not work on XP unless you have the XP CSE installed. Even with the CSE many people have reported "issues" with them working reliably. GPP is not available for older OSes than XP SP2.

Edit:
Here's a copy of the MapDrives.vbs script we use. Works flawlessly on WinXP/Vista/7/2003/2008/R2.

' Author: Chris Stone
' Date: 29 MAY 2009  Version: 1.3
' Purpose: Map network drives

On Error Resume Next
Set objNet = CreateObject("WScript.Network")

Public Sub CheckAndMapNetDrive(Letter, Path, Persist)
    'Check if drive letter is already used
    Set colNetDrives = objNet.EnumNetworkDrives
    For i = 0 To colNetDrives.Count - 1 Step 2
        If colNetDrives.Item(i) = Letter Then
            'Drive Letter Exists, Test if it's the same Path
            If colNetDrives.Item(i+1) = Path Then
                'It's the same, no new mapping necessary.
                Exit Sub
            Else
                'It's different, remove old.
                objNet.RemoveNetworkDrive colNetDrives.Item(i)
            End If
        End If
    Next
    'Drive does not exist now, never did or removed.
    objNet.MapNetworkDrive Letter, Path, Persist
End Sub 

CheckAndMapNetDrive "X:", "\\server\share1", True
CheckAndMapNetDrive "Y:", "\\server\share2", True