Just a small topic really, but I noticed a few things in the Alloy of Law that suggest Miles is not a natural twinborn but actually a compounding hemalurgist. I'm not sure if this would have any lasting effects on the trilology, but it does explain some of Miles' behaviour. Here are the points.
1) Metalminds: Miles has metalminds driven into his skin as well as in his body. Only contact is needed with the metal for feruchemy while hemalurgy needs contact with the blood. Of course, there are two problems with this; Miles consumes his metalminds in compounding and Miles still has his powers when the constables strip him of his metalminds. The solution to these problems are that Miles' hemalurgic spike(s) (multiple spikes might explain why he can heal so quickly, as compounding might not even be capable of this) and that because they are pierced inside his body he would not use them for compounding anyway.
2) Change in behaviour: Miles turns from a devoted (though ruthless) lawkeeper to an outright criminal. A quote from Ranette on page 235 shows the unusual change in Miles' views.
The scene where Miles uses his powers as an augur also shows the unusual path that he has followed.
3) Miles' death scene: While he is gunned down by the firing squad, he shouts out about 'the bears of the final metal'. I have no idea who the bearers are but the manner in which Miles says this, especially as it is in his final moments, sounds like something that would come from a more powerful force controlling him.
So from what I've seen, it looks like Miles was spiked early on in his life without knowing, perhaps so that he could be later controlled by a powerful force. This force would have caused him to later commit the actions he does within the Alloy of Law, when he finally succumbs to the influence of the being using his hemalurgic spikes against him. Perhaps Miles' growing bitterness was similar to Vin's doubts about Elend, in this case causing Miles to increasingly hate modern civilisation on Scadrial.