Wow, I just logged back in.
Glad I could be of help.
To be a little more specific about our trip:
Went to AK the first Sat, MK the first Sun. Heaven -- hardly any lines. Nothing was over 20 minutes (I think we went on "It's a Small World" 3 times in 30 minutes -- my three year old DD could not get enough of it!) Even during that week, same story (a little busier midweek at MGM, but still able to see everything). We would get fast-pass tickets about 3-4 times each day for different rides, ride another ride, and go back to use the fast pass (could have done this more often, but we had a group of 11 to keep together!).
MK on Feb 14 was twice to three times the crowd, raining, and no one left! We could do one fast pass in the morning, possibly a second if we pushed it (we didn't), but by the mid afternoon, wait times were close to closing (and the weather did not permit us to hand around). We were a little disappointed (granted, to the seasoned WDW traveler, the crowds may have been "normal," and we were just spoiled), so we went shopping at DTD the next day. Again, twice the crowds, twice the wait to eat.
I cannot comment on December or January (sorry -- we've only ever done February!), but I can say the lack of crowds SO makes up for the shorter hours! Totally worth it on the off-season, and I highly recommend it. (I am not one to drag children out of school to travel, but this was a reunion. Once we did it, though, I'm not sure I can go back to a busier season!)
Fink26 is right about the weather -- very iffy this time of year (but no comparison to where we came from!).
Have fun at SSR!