First of all, I thought the length of the game was perfect, and I really liked the list of tasks and the system of building the presents once I understood what to do.
Most puzzles were a really good level of difficulty - not too easy or too difficult. There were only two puzzles where I needed hints, and it looks like they were the same ones that everyone else struggled with - finding the light source and reaching the gingerbread. The first was easy once I checked the in-game hints, but the second had me utterly flummoxed. I was going around all over the place trying in vain to move chairs and tables and ladders to find something to stand on. I had already built the toy you're supposed to use and had put it on the sleigh, and it would never have occurred to me that I would need to use it again (and temporarily minus my points for taking it off the sleigh!). Because of the nature of the list, I assumed it was 'job done' once presents were on the sleigh.
(I was even trying to build non-requested items from the book in the vain hope that they would help me reach the gingerbread - the stern message about not wasting time was pretty frustrating there!)
Because the items you can interact with are quite fluid (some conspicuous, some not) I found a lot of instances where you can't interact in some ways with inconspicuous items (e.g. if you try to 'get on' the counter in Fabric Supplies, the game says 'you can't see a counter' or similar).
The only serious error I noticed was that if you try to examine the toys in Toy Storage, it says 'you can't see a dump here!'
Overall, I thought the toy-building mechanic was a real strength and was really fun.