Even though I like to talk about the most recent major releases of SQL Server, there are still plenty of organizations running SQL Server 2008, which was a good, solid release of the product, with many improvements over SQL Server 2005. Lets assume that you have been pretty diligent about keeping your SQL Server 2008 instances up-to-date with Service Packs and Cumulative Updates, so you find yourself on SQL Server 2008 SP3 CU5 (Build 10.0.5785), which was released back on May 21, 2012. Actually, you should be pretty proud to only be on a build that is about seven months old, since I regularly see people running builds so old that they are on “unsupported service pack” levels, often being 18-24 months old.
You want some specific justification and ammunition for applying the latest SQL Server 2008 SP3 Cumulative Update, which is CU8 (Build 10.0.5828), that was released on November 19, 2012. You could read the fix-lists for each cumulative update since SP3 CU5, available from this master CU list article from Microsoft:The SQL Server 2008 builds that were released after SQL Server 2008 Service Pack 3 was released
Or, you can start out with this filtered list that I put together:
SQL Server 2008 SP3 CU6 (10.0.5788) July 16, 2012
FIX: Errors when a client application sends an attention signal to SQL Server 2008 or SQL Server 2008 R2
FIX: SQL Server 2008 R2 or SQL Server 2008 stops responding and a “Non-yielding Scheduler” error is logged
FIX: Incorrect results are returned when you run a query that uses parallelism in the query execution plan in SQL Server 2008
SQL Server 2008 SP3 CU7 (10.0.5794) September 17, 2012
FIX: Error messages when you use dtexec to execute packages in SQL Server 2008 Integration Services
FIX: SQL Server Agent job fails if you set the job schedule type as “Start automatically when SQL Server Agent starts” in SQL Server 2008 SP2, SQL Server 2008 SP3 or SQL Server 2008 R2 SP2
FIX: Poor performance when you run a query that contains correlated AND predicates in SQL Server 2008 or in SQL Server 2008 R2 or in SQL Server 2012
SQL Server 2008 SP3 CU8 (10.0.5828) November 19, 2012
FIX: Memory leak if you enable the AUTO_UPDATE_STATISTICS_ASYNC statistics option in SQL Server 2008
FIX: Large queries that modify data run slower than expected when many locks accumulate in a SQL Server 2008 R2
Most of those hotfixes seem pretty significant to me (and this is just the subset that I picked). I strongly encourage you to start reading the hotfix list when new cumulative updates are released, because there is a lot of good information there. SQL Server 2008 SP3 CU9 should be released around January 21, 2013, which is good timing after the holiday freezes and quiet periods for many organizations are over.