I was at DLR last year from 12/4 - 12/8. There was a CP on Sunday, 12/4, but I didn't really notice a large increase in crowds until mid-to-late afternoon. However, I did notice quite a few more people buzzing around the hotel lobby than there normally would be.
On Monday, 12/5 it was delightful in both parks. This was probably due in part to some heavy wind that blew through town for a few hours and then disappeared, but DCA was like a ghost town and even Disneyland was not bad. Main Street was not crowded. There was no line at Gibson Girl Ice Cream (shockingly). It was good because I think all the CP people cleared out and left the parks to be downright reasonable. December 6th was a bit more crowded, but not the worst I've seen. December 7th was not bad at all in DCA in the brief time I was there. I'm not sure about 12/8.
This year, however, who knows what will happen? First of all, the Halloween Time season (and the Halloween Parties), by most accounts, has already been quite crowded for the last few weeks. I think that California Adventure's makeover/"re-imagining" is still bringing in the crowds. This will certainly not change by the holidays, which is peak season to begin with.
Then, having the CP on 20 nights in December instead of 2 nights is uncharted territory for DLR. We really have no clue whatsoever how this will impact crowds. We don't have a real DLR-specific template that we can use for a guideline. It's not like they just increased it from 2 nights to 5 nights. They (DLR) are taking a huge leap in having the CP on 20 nights. That is major. This could either end up being utter madness in terms of crowds all through the normally slower days in December, or it could be okay. Maybe the CP won't be as huge of a draw as Disney is hoping.
