Has anyone out there used portions of Call of Cthulhu's magic system in D&D? It seemed like a weird idea first, but if one were aiming for a Conan-esc Sword and Sorcery feel it seems like it would be just right. Half-mad Necromancers summoning demon-gods that wreak havoc and cause gruesome death to all they encounter seems to fit into both categories nicely.
There are a couple of options if one chose to go this route as well. You could pair d20 Cthulhu with a 3rd edition D&D or Pathfinder game and because they both use the same base mechanics they would likely fit together pretty well. I don't have much experience with the d20 Cthulhu rules and I've heard conflicting reports about their quality but it certainly is a streamlined option. Alternatively you could pair old school D&D and traditional Call of Cthulhu, though the rules would take some tweaking to fit together.
The more I read of the Cthulhu magic system the more I like its dark and ominous feel. That having been said, I'm not sure it would encourage people to play Magic Users in games if they had to deal with the added danger of going insane through spell use.
Has anyone out there tried to pair D&D and CoC magic? What worked and what didn't? Please feel free to share any sage wisdom you have.