During one of the sessions today on storage sprawl the speaker recommended a three tiered storage architecture. He suggested:
Tier 3: OS images; SATA storage
Tier 2: General application data and binaries; FC storage
Tier 1: Page files and databases; FC storage
His rationale was once an OS is booted, very few I/Os occur on the OS volume, so it can easily live on SATA storage. Tier one and two require more IOPS, and thus probably need higher speed and more expensive FC storage. If you use SRM, that will likely impact your tier design as it has some restriction on datastore architecture. At the very least, his three tier architecture is something to consider.