While trying to help on the ConfigMgr forums the other day I found this useful, but some what random piece of information:
Windows 7 & Server 2008 R2 cannot join a Windows 2000 Domain via a script if an OU is specified.
This will obviously cause problems if you're using a task sequence to join either of these OS's to a 2000 level domain and specify an OU.
More information can be found at http://support.microsoft.com/kb/979645
SP1 is at Beta 1 at the time of writing but for more information on the currently included patches in the upcoming SP1 for Windows 7 & Server 2008 R2 have a look here: http://technet.microsoft.com/en-us/library/ff817572(WS.10).aspx