Surprisingly enough, xxxHolic is the first request I've had for a Clamp review. For those of you who aren't familiar with the group, they're an all female group who started out writing doujinshi before moving on to professional work in 1987. They've been fairly prolific, but their end products tend to range considerably in quality. Some being spectacular, others being terrible. xxxHolic leans toward the latter.
xxxHolic is an anime that doesn't have an underlying plot so much as a series of loosely connected episodes that are all based off of Japanese folk lore. A young man named Watanuki can see spirits. He finds a shop that grants wishes and ends up working there part time. Shenanigans ensue. Most of the episodes have only very loose connections to each other. An anime can be setup like this and still be well done, but xxxholic isn't. One major issue that pops up multiple times is that serious moments, which should have some impact on the characters or the plots to come, are dropped and never mentioned again instead. Another issue is that the episodes don't really do anything interesting with the folklore. Instead it just throws the reference at you, follows up with some faux intellectual statement to wrap things up and moves on to the next thing. The comedic aspect is another area where it fails since there are very few moments that are actually funny. Most of the humour is based on Watanuki having really over the top reactions to what's going on and it's not particularly funny when they do it the first time. So doing it multiple times every bloody episode just gets repetitive and really boring. The semi-serious moments they try to have are also ruined by them always reverting to "comedy" quickly after those moments end.
The characters certainly don't make up for the largely absent plot. Each one has one or two exaggerated personality traits that define them. Watanuki over-reacts to things and is a tool. Doumeki helps Watanuki and has no visible reaction to anything. Himawari either doesn't understand the obvious or toys with Watanuki for fun. Yuuko always knows what's happening but only deals with issues personally when she has too. She also drinks a lot. And I just described the four major characters completely with a few adjectives. I could do the same for the secondary characters, but that would take a while. One other issue with the characters is that there are several plot lines involving individual characters that seem like they could potentially lead to development, but they either get dropped or go unresolved in favour of keeping the status quo.
The art is terrible. I'm used to borked proportions in anime, but xxxHolic just takes it too far. The characters have ludicrously long and slim limbs and bodies with tiny little heads. This makes them look more like models made out of string cheese than actual people. The backgrounds are generally sparse and the supernatural beings don't have much impact. They just look bland most of the time.
The voice work is difficult to judge. There are a lot of really talented voice actors working on this such as Nakai Kazuya, Ohara Sayaka, Itou Shizuka and Fukuyama Jun but they all adopt these really exaggerated voices which add to the lack of depth for their characters. I blame the direction since I know that all of them can do roles with depth. The music ranges from bad to generic.
The yuri factor is a 2.4/10. Simply because Yuuko gets really touchy with some of the other female characters and it comes off as a bit homoerotic.
My final rating for xxxHolic is a 3/10. The art is bad. The characters have no depth. It's not funny and what little story there is lacks interesting content. If you want a good anime grounded in Japanese myths there are far better options like Mushishi or Kino's Journey. If you want something by Clamp specifically there are still better anime, like Magic Knight Rayearth or Cardcaptor Sakura. As for xxxHolic, you can skip it.