So far I've never had a cat that messed with Christmas stuff (I pretty much always have a cat living with me, so I've been lucky).
However, our new cat Lucy? I'm betting she's going to be an issue. The tree has been up for a week but not decorated (I have not had time this week to do it in the evenings when I get home from work). She ignored the tree for the first few days but recently has been very interested in it. I'm going to bring out a squirt bottle soon.
It's also anchored to the windows so if she does jump on it, it won't fall down (I really hope). It's anchored in two spots. (And by anchored to windows I mean to the blinds that are cement screwed into the cinderblock walls, and I have steel crank out windows so the other part is anchored to the screws that hold the "lock" in place).