Here's how I do it:
>Shoot raw(won't work with jpeg I think)
>ISO 100 expose for the higlights(ETTR) using the raw histogram
>Choose dual iso from magic lantern menu and set it to 100/800
>Process the files using cr2hdr.exe
>Edit in Lightroom
It's good for some situations where you need to raise the shadows.
http://www.magiclantern.fm/forum/index.php?topic=7139.0