As you may be aware about new features within SQL Server 2008, one of the them is Resource Governor which is a feature than you can use to manage SQL Server workload and system resource consumption. It will enable you to specify limits on the amount of CPU and memory that incoming application requests...
Have you ever asked this question about how do I identify the queries that worth tuning? The simple answer it is neither easy or hard to obtain such information if you have managed your SQL Server by deploying industry best practices (wherever possible). Then it comes what kind of practice you should...