I see most opinions of Sanderson's work are based on the Mistborn trilogy and Elantris, but no mention of Alcatraz Versus The Evil Librarians? I know it's a children's series, but since we're assessing his evolution as a writer I think it's important to bring it up.
For example, It's clear in the Mistborn books that he can't handle quite as many characters as say, Mercedes Lackey (she got me into the genre, I've yet to catch up to everything you guys are reading - believe me, I'm taking notes), so there are less main characters/personalities in Avs.TEL.
However one of his strong points is messing with the reader's head (his organization in magic is really good, you have to admit) and there is plenty of that mixed in with good humor
Another improvement in his development as a writer I noted is the fact that where he stalled with The Well of Ascention before finally getting to the important info in The Hero of Ages, he seems to be playing it by ear more so as to deliver something with each installment in the Alcatraz series. Of course I can't say that 100% seeing as he's planning on two more books or so.