I went last year on the Wednesday and Thursday after Thanksgiving (Nov. 29 & 30).
Crowds were very light. I was able to walk on HM, Buzz and Mr. Toad multiple times. Wait times elsewhere (POTC, IASW, BTMR) were maybe 5 minutes. Even Indy and Space Mountain only had posted wait times of about 15 minutes (though I still FastPass'd them). I think the longest I waited for anything was for Peter Pan - about 15 minutes mid-day! DCA was so quiet, there were only 8 of us plunging in the elevator at Tower of Terror.
I'm planning on going at the same time this year, and have already made my room reservations. Based upon my experience, it's the perfect time to experience DLR decked out for the Holidays, but without the crowds!