I continually run into resistance when discussing the idea of ditching the SAN and using direct attached storage (DAS) for Exchange 2010 implementations. There are a number of reasons that are thrown out there ranging from reliability to managability. However, in my opinion, in most cases, all of those issues can be overcome. At the very least you owe it to yourself and your organization to consider the possibility of saving some large $$ by implemementing multiple data copies in a database availability group (DAG) with DAS rather than using an expensive SAN.
This is one of the best posts I've seen regarding storage for Exchange 2010: http://msexchangeteam.com/archive/2011/01/07/457471.aspx