I suppose I'll start with the negative, just to get it out of the way (and really there isn't a lot to complain about here, this was a great mission, especially for a speedbuild!). The first is major performance issues, which has already been brought up by other folks. I haven't seen my frame rate take that much of a swan dive since the caves in No Honor Among Thieves, but I have an aging HP Pavilion Slimline that really doesn't do well with gaming, so a lot of this is on my end.
Secondly, a pretty tiny nitpick, but I found myself having a bit of trouble with the church roof. It took me awhile to figure out you're not supposed to get in through the belfry, even though it looks like you should be able to mantle onto the gargoyles, then the big hammer, then finally get in through the busted bars. Just something for your consideration.
Finally, the woman's voice at the clothier's was a bit confusing, and I never did find out what the deal with that was. It did, however, prompt me to look around further, which is what led me to find the key I needed, so I guess it served its purpose?
In terms of visuals, this was a great-looking mission with good use of space. The climbing bits added a nice level of verticality, and the overall flow of the mission seemed pretty intuitive. The difficulty also felt pretty balanced, as the zombies, while an ever-present threat, aren't too difficult to get around if you're careful.
I especially loved some of the little details you threw in, for example the hidden compartments in the church. Usually things like that are just McGuffins solely for the player to go find and raid, but incorporating them into the plot like you did added some extra life to the world and story (or so I felt - it seemed like a nice change of pace). Also, the burned stake out front and the note explaining it was delightfully macabre. Definite points for that!