One thing that I found really annoying when doing a sysprep was my drive letters changing. In some environments, drive letters need to remain constant when the machine is being deployed/cloned. Unfortunately, I don't have too awful much experience with sysprep's new unattended.xml file and there doesn't seem to be any clear cut tutorials on how to do this, so I found a nice workaround.
To prevent the drive letters from chaning, use the following steps.
1. Open up the registry (Start->Run->regedit)
2. Navigate to HKEY_LOCAL_MACHINE\System\MountedDrives
3. Make a backup of this. File->Export (save to a place where you can access it soon).
4. Make sure you leave regedit open and run sysprep via command line. Use the /quit switch when running sysprep as we do not want to restart the machine yet.
5. Once sysprep finishes, go back to the registry editor.
6. Import your registry backup. File->Import
7. Restart/Shutdown the machine and deploy
Credit to this answer goes to jthiessn for finding this trick. Make sure to "up" his answer on the Microsoft forum for his fine work 🙂 http://social.technet.microsoft.com/forums/en-US/itprovistadeployment/thread/694daccd-a48d-4529-9aaa-555cda297038