- Feruchemists are really powerful if you let them have too long to charge up - the best way of dealing with this being that they get cracked down on hard by the Inquisition if they "hulk out" in public.
It looks like the rules will get tweaked here so that you must tap 5 charges to get any Nudges with Feruchemy, instead of the standard 1d per 1 free Nudge above 10d.
Feruchemists remain awesome, but they are not as powerful against powerful opponents and the natural restrictions of storage times, social stigma and Terrisman pacifism should become more compelling.
- Pewter is much better than most other Mistings in combat because it adds to your roll instead of replacing it - while Pewter is the "combat metal", it seems a little off that the Coinshot gets a dice pool of 6 and the Thug gets a pool of 11 as starting characters
Well, Pewter is cool in the books too.This will be more true if you focus on combat. Fortunately, the Mistborn RPG allows for a much wider scope of conflict.
On saying that Coinshots are cool too, if not cooler. Try steel pushing your way onto a spire and coinshoot the Thug all day long

Ranged attacks have a real advantage and when you combine it with Steel’s manoeuvrability (with Steel Running stunt, the Pewterarm will never catch the Coinshot), you realise Pewter is only really good in certain situation.
Plus steelpushing can effect multiple targets with a Stunt. If Pewter wasnt so cool, it would be quickly redundant.
- Having a good Physique doesn't seem to help with Steelpushing - you can't make a really buff Coinshot and win Pushing contests just by being heavier. In fact, how hard you are to move doesn't figure into a Steelpushing contest.
That’s right. The main factor is weight and those rules for iron pulling and steel pushing are immutable. Pewter will assist you survive being flung away on a crazy steel push, but that’s about it. This is consistent with the books.
- Buying extra vials of metal (say, if you know you'll need more than you usually carry for a job) - is that a Resources check?
Yes. And remember extra vials are not props so they disappear at the next long breather if unused. So no stockpiling of metal vials is allowed

Costs are listed on page 237.
- If a player wants to be a Seer or Mistborn (we don't have one, but they have had some contact with friendly ones), surely they can't take a vial of Atium as a prop? Is there any way to replenish your supply without stealing it from nobles or the Lord Ruler?
Atium is not listed on the items that can be taken as props on pages 109 and 110. They are listed on page 237, so you can buy them with Resources (though the Difficulty is 5!)