Microsoft SQL Server 2008 Service Pack 3 (SP3) is now available for download. While keeping product changes contained, we have made significant investments to ease deployment and management of Service Packs. A few key enhancements for customers in Microsoft SQL Server 2008 Service Pack 3 are :

Enhanced upgrade experience from previous versions of SQL Server to SQL Server 2008 SP3. In addition, we have increased the performance & reliability of the setup experience.
In SQL Server Integration Services logs will now show the total number of rows sent in Data Flows.
Enhanced warning messages when creating the maintenance plan if the Shrink Database option is enabled.
Resolving database issue with transparent data encryption enabled and making it available even if certificate is dropped.
Optimized query outcomes when indexed Spatial Data Type column is referenced by DTA (Database Tuning Advisor).
Superior user experience with Sequence Functions (e.g Row_Numbers()) in a Parallel execution plan.

Microsoft SQL Server 2008 Service Pack 2 is not a prerequisite for installing SQL Server 2008 Service Pack3. These packages may be used to upgrade any of the following editions of SQL Server 2008:
Enterprise
Standard
Evaluation
Developer
Workgroup

SQL Server 2008 SP3 contains the cumulative updates of SQL Server 2008 SP2 cumulative update package 1 to 4, and fixes to issues that have been reported through our customer feedback platforms. These include supportability enhancements and issues that have been reported through Windows Error Reporting.


Note: To obtain SQL Server 2008 SP3 for Express Edition or Express Edition with Advanced Services, please go here.
For a detailed list of new features and improvements that are included in SQL Server 2008 SP3, review the Release Notes.