The primary reason why I bought the new Mistborn paperbacks was to see if there was a MB3 sample chapter. The new MB1 does.
And it has a very interesting piece of information regarding Allomancy. Basically, the chapter is about Spook and how having Tin on basically a year straight (it appears the time between 2 and 3 is another year). It says... his powers have been enhanced far beyond the powers of a normal Allomancer.
I'm going to quote some multiple paragraphs, but since Brandon says on the MB2 paperback that its posted on his site (it isn't, unless I just can't find it, but I presume Brandon intends to post it), I figure it would be okay:
To Spook, however, they [the mists] were barely an obstruction anymore. He'd always been told not to flare his tin too much; he'd been warned not to become dependent upon it. It would dangerous things to his body, people said. And, the truth was, they were right. He had flared his tin nonstop for a year straight--never letting up, keeping his body in a constant state of super-heightened senses--and it had changed him...
Somehow, by flaring tin for so long, he had permanently enhanced his senses to a point far beyond what other Allomancers could attain.
This explains a ton. First off, it explains one reason why Inquisitors have an incredible power to see with Steel (which, Brandon says in annotation that any Allomancer can learn to do). Obviously, the Inquisitors would constantly be burning steel or iron whenever they are awake. Such would have a permenant effect on the Inquisitors' eyesight, making them much more powerful.
Likewise, with the Lord Ruler and his Soothing, constantly Soothing from Kredik Shaw would change his abilities far beyond the power of a normal Allomancer...
Now, for the Inquisitors, this is just more evidence they actually use Allomancy, not some weird Hemalurgy for their eyesight.