Revenant (3/30/2010)
Well, the question is incorrect, anyway - RG is also available in the Evaluation Edition. So that "only" without this version mentioned is IMO misleading.
Not all that misleading though eh?
http://www.microsoft.com/sqlserver/2005/en/us/trial-software.aspx
http://www.microsoft.com/sqlserver/2008/en/us/trial-software.aspx
Both explicitly state that it is Enterprise Edition that you are evaluating.
Paul White
SQLPerformance.com
SQLkiwi blog
@SQL_Kiwi