Here at the NY Microsoft Technology Center (NY MTC), we recently ran a series of SQL Server Upgrade/Application Compatibility Labs with various customers and ISVs.
To learn more about the labs, watch this video blog entry shot during one of the actual labs: http://blogs.msdn.com/mtcny/pages/sql-server-2008-upgrade-lab-april-2008.aspx.
The two tools used in these labs were SQL Server Upgrade Advisor and SQL Server Upgrade Assistant.
SQL Server Upgrade Advisor helps you prepare for upgrades to SQL Server 2008. Upgrade Advisor analyzes installed components from earlier versions of SQL Server, and then generates a report that identifies issues to fix either before or after you upgrade. Additional information on the Upgrade Advisor can be found here: http://msdn.microsoft.com/en-us/library/ms144256(SQL.100).aspx.
SQL Server Upgrade Assistant (SSUA) is a tool made available as a free download from Scalability Experts. The tool can be downloaded at the following link: http://www.scalabilityexperts.com/default.asp?action=article&ID=43 . SSUA uses traces to allow an IT professional to evaluate the behavior of an application on different versions, service pack levels, editions, or configurations of SQL Server. The tool can even be used to test the behavior of different version of an application release when a hotfix or service pack is installed on SQL Server. SQL Server Upgrade Assistant currently supports upgrading SQL Server 7.0 and SQL Server 2000 to SQL Server 2005, as well as supports SQL Server 2000 and SQL Server 2005 to SQL Server 2008.