I liked that Sanderson's system in Mistborn was unique and interesting; I didn't like that he got down to the cog-level in telling you how it worked. Magic has to have some mystery for me, and if it's just a set of builds/adds that you can slap on a character for a period of time, I lose that sense. I think he did some very interesting things, but the sheer internal-ness and game-feel of it ultimately caused me to go "meh" by the end of the book. (I had other issues, too, but we're talking magic here, so I'll stick to that.
Now PVBrett's I like. There's mystery and power and consequences there beyond "you will get tired, etc." to it. Glyph magic isn't exactly new, but he took it in an interesting direction and, more importantly, built a world around it where it had a dynamic impact.
I think Chaos magic in Zelazny's Amber universe was interesting. It got a little too twitchy at times, but overall the idea of using a core power of the universe to manipulate your reality hit pretty true to home in what magic kind of should be. You got a sense of where it came from, although I think there could have been more risk/cost involved.
As may be obvious, I'm not as big on building clock-work magic systems as some other writers. Give me a reasonable premise and a sense of wonder, and I'm usually willing to go along for the ride. Even Tolkien's stuff didn't bother me too much since you were essentially talking about mythic/saga type magic at that point, and in those tales there's no consistency in the magic to begin with (I mean, have your read
any Icelandic sagas? The Mabinogion? Older fairy tales? A person has earth-rending power one verse, and is brought low by a thrown rock in the next. Crazy, great stuff.). I think we got a lot more worried about the "How" behind magic when RPGs and the like gained traction, since by definition, you have to have rules for a magic system in a game. Prior to that, magic was more like the stuff from legends and myth; after, we got more into the clock-work/dice-rolling type of magic in SFF.