The report which evaluates the different RDBMS vendors is available. In the report all the vendors providing relational database management systems have been evaluated, it is exhauastive in terms of the various factors which went to examining the different RDBMS offerings. In particular emphasis related to Microsoft SQL Server, here is a Quote from the report:
Microsoft: The most aggressive DBMS vendor with a strong road map. Microsoft has done reasonably well in the database business but over the past three years has shown increasing focus and commitment to going after the enterprise market. SQL Server 2005 and, more recently, SQL Server 2008 have enabled Microsoft to take market share in moderately sized to large enterprises, delivering good performance, scalability, security, and availability functionality. Five years ago, hardly any enterprises ran multiterabyte databases with SQL Server to support critical applications. Today, hundreds of enterprises are running 10-terabyte and larger transactional SQL Server databases.
For a complete read on the report: Use the link mentioned below