747b0392__5_1___Postgres_OnLine_Journal__Microsoft_SQL_Server_2008
[Feature] Drivers already installed on Windows [MySQL 5.1] No [PostgreSQL 8.4] No [Microsoft SQL Server 2008] 
Yes - when you have a windows shop this is huge especially when you are not allowed to install stuff on client desktops and you need to integrate seamlessly with desktop apps. This is why using SQL Server Linked Server to get at yummy features of PostgreSQL comes in handy.
Cross Compare of PostgreSQL 8.4, SQL Server 2008, MySQL 5.1 - Postgres OnLine Journal
Microsoft SQL Server 2008