The only real difference is the way in which you migrate the public folders.
Transitioning from Exchange 2007 (SBS2008) requires the MoveAllReplicas script from the Exchange Management Shell as per:
http://technet.microsoft.com/en-us/library/bb331970.aspx whilst this will also work with Exchange 2003 it's easier to use the method in my article. Unfortunately that won't work for 2007 so you need to use this script.
