Is this good made in advance? (Refrigerate?) Is it best served cold or room temp?

You can leave it out for a day...just cover with plastic wrap. I have done this and the texture is fine, even two days later. It is best room temperature, in my opinion.

Thanks! I made the crust yesterday & decided I have enough time to bake it today. I'm excited/anxious to try the recipe... hope i don't ruin Christmas Eve dinner!

Dymnyno would have the best answer but based on the recipe it seems you could make this the day before and refrigerate it. If it stays too long in the fridge the crust will become soggy and the lemon filling will begin to "weep." I would take it out of the fridge at least 15 min before serving. It will taste good cold (but not too cold) as well as at room temp.