Even though the official release is only tomorrow, the first OAD of XXXHOLiC Shunmuki appeared earlier today on the japanese video streaming website NicoNico Douga. I have ripped the video file (.mp4) and uploaded it to Media Fire.
I liked the OP a lot, and the animation quality is very high, indeed more than the TV anime but a bit less than the movie. I was actually surprised to see a manga arc I wasn’t expecting to see.
Looking forward to the subbed version to notice bigger differences between the manga and the OAD.
EDIT: The official website of the OADs added a report from the early screening of XXXHOLiC Shunmuki that happened at the end of January.