It was unexpectedly good, given that I didn't expect much.
The story is solely Watanuki-centric, and it's a logical choice because it's a movie, not a series.
Kamiki Ryunosuke acting is perfect, his Watanuki is pretty believable and sympathizable. I wasn't sure about Shibasaki Ko as Yuko after seeing the photos, but she actually fits. Their relationships are a bit cut up because obviously they should have sacrificed something, and Yuko and Watanuki relationships are built on many client cases. So, yeah... There is a slight disbalance, but I consider it to be a companion movie to the original manga, so I'm okay with it.
Also, I loved how visuals and music mix together to show the bizarreness of the story. I think, without them, this movie wouldn't work half as well as it did.
Overall, I would definitely recommend it to dive into the nostalgia for the original xxxHolic.