It's a nice time to go, very nice. We've been twice during this time period.
The last time was this past Dec. 1st-5th.
The Unofficial Guide is right on all counts. The one thing I would be prepared for is chilly weather. While you can have nice, warm days (upper 60's to low 80's) they are not that often. The first time we went during this time the daytime
highs were in the 40's, and the nights were darn cold.
This last December, the first two days were cold (again, 40's and 50's) with the nights colder, but the last couple of days were in the upper 70's.
MVMCP is a lot of fun, and WDW does limit the number of tickets sold per night. The weekend nights can sell out and can therefore be more crowded than the other nights. I would recommend getting tickets for a non-weekend night.
This year they had an area where kids could dance (to music from a DJ) with the Christmas reindeer from the parade! Made me wish I had a little one to do this with again!
Definitely go and have a wonderful time!