We have a 2005 cluster, and two standalone 2005 boxes for reporting, as well as a few 2000 boxes. All are enterprise version. The 2005 boxes do not seem to have a really compelling reason to upgrade at this time; however, the 2000 boxes were slated for upgrade to 2005. At this point, we're looking to leapfrog and go straight to 2008 next year...I'm sure that'll be just in time for the next release of SQL Server - so we'll be behind the curve one more time!