I know the advantages of upgrading from sql server 2005 to sql server 2008, but upper management could care less about t-sql debugging, intellisense, the merge statment, etc..., so what are some features in sql server 2008 that upper management might actually find worth while.
I suppose you could try showing them some of Microsoft's case studies that have some relevance to your company. It might give them some warm fuzzies to see that someone else has done something similar.
http://www.microsoft.com/sqlserver/2008/en/us/case-studies.aspx
Honestly, if the level of management that is deciding which database technology to buy doesn't understand t-sql debugging and intellisense then your company has the wrong people making technical decisions.
Transparent database encryption - even if the backup files get stolen (or the entire data files) the database cannot be read. Reduces the cost of data loss and embarrassing media attention.
SQL Audit - see who's doing what with the data with no 3rd party tools necessary
Policy-based management - reduce the amount of time needed to ensure the servers adhere to a defined policy.