You will love it. The decorations are amazing, and I want to go every Christmas now that I experienced it this past year (12/24-12/31.) The crowds were certainly heavy at times, but I did not think it was too bad (especially if you use FP and get up early.) My husband never liked WDW much until we went over Christmas. Now he's addicted.
It is great crowded but great.We are going Dec 8th-15th this year.You will love on the decorations,MVMCP,CP and all the live shows.Arrive early and use fast pass you will have a magical trip.