Really fun oneshot.

I ran this with two groups (5-6 lvl4 characters and 3 lvl3 charakters). Both needed a whole session (4 to 6 hours) to get to the top of the mountain. As there's too little to do for a whole 2nd session in the castle, I added a festive little dungeon replacing the entrance to the factory (resulting in almost needing a 3rd session). I'm assuming playing it with a party instead of just one player, plays the main role in terms of time here.

Both parties really took their time figuring out what was up with the coals in Cheerington. Both tried to burn them, so if you run this, might wanna be prepared for that (poor gnomes). This part is probably where I could have saved some time that was needed for the castle in the end. The fights in this part were alright. Don't underestimate the gingebread men, one of my parties had quite the trouble with them.

In the woods, the reindeer were quite the challenge for the lvl4 party, after previously encoutering the will'o'whisps. For the rested 3rd lvl party they were perfect. I really enjoyed them not provoking opportunity attacks. Made the fight some more dynamic.

One thing I would put some work in, is the castle. Belsnickle felt too weak (for a party) for what I would expect to be a bossfight. Hiy toy adds were fun as to poisoning everyone and the blinding effect had my players get a bit scared, but I would give him some of the Imps or the devil from the factory as additional adds. There's no point in fighting the Imps in the hall or the devil in the factory after already defeating their boss (in my opinion).

All in all really fun holiday adventure that can easily be adjusted for parties. Buy it and run it.