Yeah, I'd probably be somewhat less miffed if Molly had been Lady of Summer-ified, instead. Though, still miffed -- that would put her and Harry at odds more directly. As for guessing it, I saw what Mab's plan was for Sarissa once Harry told her she was coming to Demonreach. Not too terribly hard, but my gut actually expected her to not end up with Winter, though I didn't realize it at the time -- instead, I consciously thought to myself "but.. Sarissa isn't an 'M'-name..." Of course, Molly not being a changeling prevented me from following that up and making that connection ahead of time. I don't mind saying I felt just the slightest bit cheated at that sucker-punch. It's the kind of thing Butcher doesn't do very often, and that's one of the reasons I like him.
I'm hoping that what Harry's been told a few times in Cold Days about mantles not being everything extends, to some extent, to those held by the Fae themselves. If so, then perhaps Molly won't slip that much further than we've already seen (considering her recent schooling and falling apart, mentally) and can be harsh without sporting cruelty, be calculating without being coldly so, and bring some element of her darn good upbringing and early education to Winter.
Perhaps, also, we've been a bit lead on with regards to the norm for the Lady of Winter. After all, we don't meet Maeve until after Lea gets corrupted, so it could be that we've never seen an untainted Lady of Winter.
The other thing that strikes me is that Molly could well be more powerful than Maeve, since she's got the training with mortal magic in addition to whatever Fae talents she'll pick up. I'm assuming she'll essentially lose access to her mortal magic (though the training could certainly cross over, especially considering her talents). In any event, since there was no indication that Sarissa is gifted in the Art at all, she's probably got a head start on Sarissa -- and that's the point of where I was trying to go...
If Molly's head start shakes out as useful, then Winter's got an edge.. Perhaps a bigger one than it had before. (And Mab not having to keep one eye on Maeve on the home front certainly helps in any event) This will probably prove useful in the conflict with the Outsiders -- weakening Summer without weakening Winter means Winter can shift some of its forces/focus on the home front towards the Outer Gates as things get hairy.
Pardon the pun.
I, too, am definitely curious about Mac. Whatever he is, the fact that it wouldn't kick in until the bullet was removed might be a clue. I give low, but reasonable, odds that 'Mac' might be short for something that helps, too, rather than simply a Scottish/Irish patronymic.
The Kringle reveal blew my mind, and had me grinning from ear to ear. It made me wonder, though -- I don't remember seeing the Erlking in a similar other role; but Harry made a few comments that made me wonder if I was missing something, there.