Here's a handy article I found on the Apple OS X Server RSS Feed regarding how to have your Snow Leopard server host Lion updates.
"Mac OS X Server v10.6: Hosting Software Updates for OS X Lion or Lion Server"
http://support.apple.com/kb/HT4771
This is especially useful for someone like myself who is not ready to make the leap to Lion Server, and, only has one SUS for serving updates.
Enjoy!
--
Ted August
Salve Regina University
