I actually had it in there at one point. But it was MS's "Mr. fix it" button. And I guess it could still be. The only thing is it seemed to diminish the importance of setting to ACHI before the first restart, since the registry fix after isn't always a cure. I'll get it in there tho, (along with a couple other things I have that don't really change the substance), this WE. GL with your switcharoo mep, let us know how it works out.
It should be, the only reason it doesn't work to just flip the IDE/AHCI setting is because Windows disables drivers at install time that it doesn't need so that it boots faster. If you install in 'IDE Mode' that includes the AHCI driver, this registry setting just tells Windows it should load the driver.