One must understand that MySQL is a "plugin" architecture, where the SQL service engine is a layer over potentially many different types of engines (15+ types). This is a feature and a bug. Only one of these engines was advertised as ACID compliant (INNODB), and MySQL did not even own that engine.
To counter Oracle's purchase of INNODB, MySQL hired Jim Starke to help them develop the Falcon engine for MySQL 6. Alpha versions of this have had some performance issues though. I wonder how much effort was taken away from the 5.1 product line to help build 6.0? I can't imagine that's a 1 man job to create a new database engine plugin that's expected to be enterprise class.
While there may be some people who move from MySQL to SQL Server, I imagine people in that area would be more likely to move towards PostgreSQL, Firebird, or one of the other open source databases out there. Both of those are full featured databases that have ACID compliance, enterprise capabilities, and SQL Standards for years that MySQL has only recently gained. They also both run on many platforms, so if you're running MySQL on Linux, BSD, or Solaris, you're more likely to move to a different database that can run on the same hardware/OS you already have.