RST is necessary for Windows 7, 8 and 8.1. With the default Microsoft driver, the CPU doesn't enter the deepest sleep mode, and power consumption is higher (the German c't magazine measured about 5W more with the default driver).
I don't use RAID, and i certainly won't set it up in my BIOS, sorry... I know the RST probably behaves differently in RAID mode. I'm using four HDDs as single disks, three of them will normally turn off after 30 minutes like i defined in Windows, because i rarely use them. They're all Seagate 4TB SATA drives (ST4000DM000 and a ST4000DX001).
As i said, with the RST 14.0, they don't turn off anymore. With the full RST, it's prevented by SMART data polling anyway. But with the driver, they don't turn off either, and i think it's because the appropriate ATA command is not sent to the disk. This seems like a bug to me. So it would be on Intel's part to test this, Microsoft provides the proper tools for this: "PwrTest" from the WDK.