The most important thing to have when using a SAN is a good SAN administrator. The things are convoluted pieces of equipment with a lot of options and while they work with only a little setup out of the box, tweaking it properly (especially for database servers!) is NOT something one can pick up from the Quick Start installation guide. I've had to DBA a SQL Server hooked up to a SAN when there was a mediocre admin and when there was a great admin. The admin's technical expertise makes 10x the difference in your performance on the exact same SAN hardware.