This was a great mission, shooting way past what I considered reasonable for a "speedbuild"! If I had to choose, I'd say my favourite aspect is how it captures the same feeling as the great Thief 2 FMs: always another area or secret to find; being able to sympathise with inhabitants in their little sidestories; and how it doesn't take itself too seriously.
What I also liked was how cold it felt. When you said it'd be a wholesome seasonal mission I was expecting something fuzzy warm like Thief's Holiday, but the street lanterns with their chill lights and the frozen breaths conveyed the exact opposite. Needless to say I enjoyed getting indoors to a well-stoked fireplace wherever I found one.
Lastly, that "bag" was fantastic: both the idea and the execution, and I quite enjoyed climbing all over those good-looking custom assets (maybe here'd be a good place to ask if you'd offer your custom assets to other mappers?).
Well then, many thanks to you both for this Christmas surprise, and I'd sure welcome more such cooperative projects!