Since there's already a general thread for magic systems, I guess I won't start another one...
Looking over the two posted variant magic systems, they both strike me as still being in the "magic as technology" vein - "I know Spell X, so I can cast Spell X every so often and it will function reliably, doing the exact same thing every time." The posted systems primarily focus on adjusting the "every so often" parameter, but still leave the effects just as consistent, reliable, and predictable.
My conception of magic in S&S, however, is that it's something dark, mysterious, generally unreliable, and definitely dangerous. Where it's not unreliable, the reliability comes at a heightened cost and/or increased danger. The one game I've seen which captures this feel is DCC, but it does so at the cost of requiring a dedicated 1-2 page table for each individual spell to determine what happens when you cast it. Can anyone suggest any systems which get this feel without the overhead of DCC-style effect lookups?
 ...and include it on a mechanical level instead of just relying on the GM winking and saying "this is really dangerous!" while everyone at the table knows that nothing can actually go wrong.