OK, as far as crowds at WDW the week of Christmas, well.....they were big!
We always have gone to WDW during September when the crowds are low, but we knew we would be going at a crowded time.
If this was your first time to go, I wouldn't recommend it. If you can only go one time and won't be back again for a long time, I wouldn't recommend this time. BUT, we went with the attitude that we wanted to see what Disney was like at Christmas and we had a wonderful time!
We didn't ride many rides. We knew we wanted to see the new Mickey's Philharmonic 3D show, and the line was VERY long...but we used the FAST PASS option and it worked great! We came back a couple hours later and went right in with the FAST PASS. We also used the FAST PASS for the Buzz Lightyear ride.
Disney MGM Studios wasn't too crowded the day we went (Dec. 24), but we didn't go to the Tower of Terror or the Rockin Roller Coaster (so maybe everyone was over in that direction).
Epcot was crowded, but we got to see the Candle Light Processional (standing in the back, but still worth it).
The lights are beautiful at both MK and Epcot! We had never seen the Spectromagic Parade at MK before (the lighted parade) and it was so beautiful! They don't do this in September.
We got to see the Country Bear's Chrismtas show at MK, which was also new to us! I liked it even better than the regular show.
So, I guess what I am trying to say is that if you go at Christmas time, go with the idea that it will be crowded, and pick the things you want to do and use the FAST PASS options as much as possible. I think it is worth going to see Disney at Chrismtas at least once. We went to several resorts to see their decorations, and they were all beautiful!
DJ