Okay, are you asking about the first week as in Dec 29-Jan 2 or Jan 5-9?
We went last year, Dec 30-Jan 4 and we had a great time. The Christmas decorations were everywhere!! Animal Kingdom was Monday and the crowds were light in the morning, but we did all the rides by 5pm. We didn't do everything as far as shows, but we did what everyone in my party wanted to do-family of 4 plus DSis. We had time to go to Epcot for supper!! Tuesday was MGM and that was a long day!! Crowds were moderate to high but we used FastPass a lot and that helped. Again we did everything the family wanted and got good seats to Fantasmic!!Wednesday-New Year's Eve we planned to relax and we did we hit Downtown Disney and then came back to resort to swim and planned O'hana's for dinner-It POURED!!!! We ate at resort and went to bed early, but very relaxed. Thursday was Magic Kingdom OH MY GOSH!!!!!!This is where all the crowds were because when we compared the crowds to the AK and MGM they were very low and MK was very crowded. I wanted this to be my favorite park but with everyone here it was hard to enjoy!!! We still had a good time because we are at WDW! Friday was Epcot and it seemed empty compared to the previous day at MK.
All in all we are going back the same time this year!!! We had a great first trip and to only have 1 day that was crowded it really wasn't bad!!