Great series!
And great suprises, the less suprising twists too.
The ending is as it should be, even a bit too picturesque-happy-ending like for me (I mean their bodies on the flowerfield, Saze mentioning talking with them in the afterlife... twice... a bit too much.). I'm absolutely OK with Vin and Elend dead and really happy that others survived.
But Sazed was my favorite character, so I may be biased.
Kandra are cool, I want more of TenSoon and MeLaan in the sequel (hope they are still immortal?). They will make a cute couple.
Marsh - I also want him in the sequel. Especially because of his numerous misfortunes in Mistborn (his brother got the girl, she died for him, he fulfilled her dream, Marsh became a mind-controlled monster and couldn't help it, got kicked by Vin, kicked by Elend, spared by Elend... and left like that. Sucks to be him.). And because of his cool Hemalurgic powers, too.
One of my big theories: contrary to what Sazed said, I still think that Feruchemy is of Preservation, and Allomancy of both. Why?
First - Preservation is not creation. It's keeping things as they are. That is why he needed to cooperate with Ruin to create. So Allomancy (positive balance) is of creation, therefore of both powers. Of Preservation is Feruchemy, which does exactly that - keeps things. Doesn't increase power, doesn't decrease power... just keeps things as they are.
Second, psychological, argument. The kandra claim to be of Preservation. The (modern) Terrismen, with similar attitude (very Conservative and lawful) are, in my opinion, also connected with Preservation. Both ancient and modern Terrisians are Feruchemists. Well, not all of them, but it's their national Metallic Art.
Allomancers tend to be much more dynamic and brutal, partially because their powers are more combat-oriented.
Allomancy is bestowed by larasium, true (however, there have been some Mistings before Ascension, not necessary because their great-...-great grandpas had used larasium). But it's mostly used to kill things, so it kind of balances itself.
Another reason - Snapping. If Allomancy was of Preservation, why would it need an extreme pain to awake? I don't know how Feruchemy first manifests, but from no mention of it in the books I guess it's rather peaceful.
OK - Preservation did Snap people (he was mad, however) so he may not be as nice as the name suggests.
However - the mist "liking" Allomancy and (probably) not reacting to Feruchemy is hard to explain with this hypothesis. And probably somewhere on the forum it is officially said that Saze was right...