I recently read the Mistborn Trilogy, and I cannot tell you how much I enjoyed the books!
I really enjoyed the story itself. The twists and turns of it kept me hooked, and I felt that the universe was well designed.
The system of magic was awesome. I have never read about another system of magic like that, so I found it to be really original and well done. It was really well defined. Even though the it was revealed to the reader slowly throughout the book, everything ended up making sense within a certain framework. It is generally one of my pet peeves when I read something containing a system of magic and get the feeling that the author is just throwing stuff in to keep things exciting, but it might introduce contradictions as the story progresses. There were no contradictions here. Everything fits together in a clearly defined way in the end. While you are reading the books you might not understand how it works but in the end of the books you will understand everything perfectly.
So I guess what I can appreciate a lot about the books is that they were well planned by the author.
I have no authority as a literary critic, but I did feel occasionally, that the way the story was told was a little too simplistic and straightforward. What I mean is that sometimes I enjoy when authors describe a setting or emotions and such, indirectly. It makes it more interesting to read than a direct statement.
Anyway, would like to hear what you guys thought about the books, if you read them. If you havn't, you should read them!