I'd say just don't expect Sanderson to turn into a writer at the peak of his skills by the end of this trilogy.

The really big step forward seems set to happen with the Stormlight Archives, his new series.

Mistborn has more going on than book 1 let suppose, but it's not that deep. It gets more complex, and more detailed, but not really "deep". It's still very much worth reading to the end, though. I guess I might say Brandon in Mistborn had better concepts than he managed with the execution (except perhaps for the magic systems, which he handles really well - he's really good with cinematic action scenes), but it remains entertaining enough none the less.

And yeah, keep an eye on the headings.

As for characterization, it's one of Sanderson's weaknesses (another are his annoying abuse of dialogue-only scenes) it's really in book 3 that there's a fairly big improvement, for some characters. Other remain a bit like cut-outs to the end.

Brandon seems to love the idea of a large cast, but so far has some problems finding ways to use them interestingly in any constant fashion (the more interesting of the bunch get better and better treatment as the books progress, though. Sazed is one, and there are others too,). For parts of the books, they seem to be there only to serve specific purposes in some scenes. In a way, Sanderson failed to give each a real story arc, they just fade in and out of the background when he needs them, and that's about it.

The politics in Mistborn remain quite black and white and simplistic to the end (it's one of the most irritating aspects of Mistborn 2, actually. It gets a bit better in Mistborn 3).