When I installed this diver, all of a sudden my CPU started running at 25%+ with no programs open, and when I disabled it, the CPU went back down to 1-2% idling. Is this driver needed/is this a known bug with this driver? I didn't find anything online.
I won't be doing any RAID systems (at least for now), so if this is the only thing this driver does I'll just keep it uninstalled.
You don't need this driver unless you intend to set up software RAID (fakeraid) using your motherboard's Intel chipset.
If you convert to fakeraid later, install the driver on your existing system just prior to installing the new drives, so that it will be more likely to boot afterward.
I know this is an old thread, but I've recently had the same question, so it's still relevant today, and the accepted answer is incorrect.
This RST driver is beneficial (though, strictly speaking, not "needed") even if you don't have RAID:
"Intel Rapid Storage Technology provides benefits to users of single drives as well. Through AHCI, storage performance is improved with Native Command Queuing (NCQ). AHCI also delivers longer battery life with Link Power Management (LPM), which can reduce the power consumption of the chipset and Serial ATA (SATA) hard drive." http://www.intel.com/support/chipsets/imsm/sb/CS-020784.htm
For example, on my Windows 10 system after I've uninstalled the driver (also thinking it was useless and after reading some responses like the one above that it's not needed), my boot time has increased from 17 seconds to 27.
I never found RST beneficial, in terms of performance, on a single AHCI HDD or SSD. In fact, in some instances, I found the Windows 10 or native OS driver to be slightly better or, if nothing else, no worse then RST.
PC makers generally consider RST a recommended but not required driver. I uninstalled it on all my Win 10 PC's just for the sake of eliminating unneeded drivers and going to a more native Windows 10 install without OEM influence. I think my PC's run much better this way but your experience may be different.
In either case I don't see a dramatic difference with or without RST.