I really liked it.
Gavilar was trying to become a Herald, and the Stormfather (or like Pagerunner said, whoever this is) was helping him!? Does this mean the Stormfather chose Dalinar as a candidate to become a Herald?
Brandon specifically mentioned Chararch's red hair, and I think that is intentional to lead us to think she is Shallan's mother. Whether or not she is we'll find out (hopefully in SA5), but I almost don't want her to be Shallan's mom. I think there is enough weirdness around Shallan's family as it is, between the Unmade, the Cryptics, the Ghostbloods, family issues.
I really really want to know what Gavilar learned from Thaidakar.
Kelsier as a seon in a trenchcoat! I love it.
What are "the most important words a man can say?" I guess swearing to become a Herald is similar to swearing to become a Radiant, which is not quite what I pictured.
I may be forgetting something from Elantris, but have we seen seons do what Kelsier's seon did in this prologue? It turned almost transparent and manipulated its form. Good to know this is possible for my Alleyverse character...
This whole prologue is crazy. I like the little bit of character it adds to Gavilar (though he's still a horrible person), and the character development for Dalinar. I think it helps with the transition from the Blackthorn to who he is in WoK.
That's all I have for now! I'm so excited for SA5.