He's broken it up into two sections: "Why Is It Important For Microsoft To Support PHP On Windows?" and "What's Wrong With The Existing MSSQL Extension For PHP?" He answers the first question by mentioning the new options that it opens up for those that want to run both Windows and PHP and still use their SQL Server databases.
Question two gives four things that he's already seen wrong with the extension including it's limited varchar support, no PDO drivers and the poor level of error reporting.
The SQL Server 2005 driver for PHP "is a PHP 5 extension that allows the reading and writing of SQL Server data from within PHP scripts. It provides a procedural interface for accessing data in all Editions of SQL Server 2005 and SQL Server 2000 (including Express Edition), and makes use of PHP features, including PHP streams to read and write large objects."