Review of Dan Da Dan

THE GOOD: Pacing and narrative flow are fantastic. This show is FAST. In fact, it's so fast that many times the ED catches you by surprise: "how is it possible that the episode is already over?" But the main appeal is that the story flows seamlessly, from one scene to the next, from one episode to the next, from one arc to the next. Despite all the crazy things that happen, none of them feels forced... which is quite a feat considering that we're talking (among other things) about ghosts, aliens, stolen "family jewels", weird powers, talking maneki-neko dolls, delusional characters, mediums that perform exorcisms using baseballbats, cows, and even romantic moments. And yet, when put together, it all works.
The animation and the direction are very dynamic, they go hand-in-hand with the flow. Visuals might not be as detailed as other shonen series, but they perfectly make up for it by conveying the necessary energy and liveliness with the animation.
Sound production is also top quality. Voice acting by all the cast is almost perfect. The music is great, and the classical music ideas used in some scenes are worth a special mention: the mixed Rossini/Orff's theme in ep. 4 and 11 is hilarious, and Mozart's guitar version theme played in ep. 5 greatly enhanced the lunch-break scene. OP and ED are as crazy as the rest of the show, and whoever contracted Creepy Nuts deserves a raise.

THE MEH:
Characters are interesting and have great chemistry but some of them are quite shallow. Even for Momo and Okarun, which are fleshed out the most, motivations are often paper-thin, and many possible conflicts are conveniently swept under the rug, at least in this first season. E.g. where are Okarun's parents? Are they really okay with him being away most of the nights? And with him having his clothes and uniforms ripped apart every other day? Etc.
Mind you, this isn't a deal breaker, since this way the story flows naturally and focuses only on the "interesting stuff", but it would be good to have at least some of these points addressed.

THE BAD:
Not much, to be honest. Someone might not like the fast pacing because it gives characters and audience very little room to breathe. But it was not a problem for me, the writing handled it nicely.
Also, you need to accept a certain level of absurdity and nonsense: this series is close to a fever dream. If you are looking for a rational, philosophical story... this is not it.

FINAL THOUGHTS:
I usually don't like shonen anime. This one, however, had me immediately invested because of its pacing and seamless flow across several ideas from different genres. Is it a masterpiece? Maybe not, but it's very good and I enjoyed it more than I expected.
Recommended if you want to experience a REALLY wild ride.