A really bad rendition of Natsume Yuujinchou meets Pokemon? I'll be honest...The only reason I watch this (and am currently watching season two) is because of Komasan (and Komajiro).
Also, since I'm being honest, I really don't like what the dub did to a lot of the catch phrases (such as Komasan). In the original version, he says "monge", and ends his sentences with "-zura" (along with Komajiro); he also sounds cute and innocent. The dub, however, made him sound like someone from the southern USA rather than the countryside of Japan, and redid his catch phrase to "oh my swirls".
So, though some people might like the dub, I'd say subtract about 5 points from sound if it's the dub version.
Youkai Watch is currently airing the second season, so I'll come back for that one when it's finished (and boy, do I have a major beef with that in the form of what has to be the most annoying character ever introduced in the anime). For now, this review will center on season one (which spans episodes 1-76).
Erm...there is no plot.
This is an episodic anime, meaning that there are typically between 2-4 short "skits" in each episode which either features special characters (Jimenken/Manjimutt in the beginning, then Komasan & Komajiro starting in episode nine) or various youkai in each one.
The overall "plot" is that, while looking for rare insects, 5th grader Keita Amano (Nathan Adams) comes across an old gachapon machine behind a shrine, and a mysterious voice urges him to "feed" the machine.
When he puts a coin in and a capsule comes out, he opens it which allows Whisper the youkai butler free. Whisper gives him the youkai watch, which allows him to see youkai which effect everyone's day to day lives.
There are two instances which contain something of a "plot"; episode 25 expands on Jibanyan's story, and episode 47 explains Whisper's background. Both episodes introduce two odd youkai who have the ability to cause time slips, though it's never really revealed what their true purpose in doing this is.
The only reason I gave the "characters" section a rating higher than "1" is due to Jibanyan, Komasan, and Komajiro...mostly the first two.
Keita Amano (Nate Adams) is a normal 11 year old boy who stumbles upon the world of youkai. To be honest, he has to be one of the worst protagonists I've ever seen; he's typically selfish, lazy, and doesn't seem to care much about the youkai even though any other kid in his position would probably love it.
Whisper is the incompetent youkai butler who tags along with Keita and knows next to nothing about youkai. He constantly has to look them up on his Youkai Pad, and always says "I've never heard of a youkai which..." whenever Keita believes something strange is the work of a youkai possessing someone.
Jibanyan is one of the characters worth watching the show for. Though he's typically seen lazing around eating chocolate bars, his full story is both sad and touching, and he has a good/helpful side to him. He takes up residence in Keita's house and seems to care more about Keita than Keita does for him.
Jimenken/Manjimutt is a pessimistic character who is honestly something of a lecher and is constantly being sent to jail. He gets his own little shorts since his introduction in episode three up until episode eight. Personal opinion...I always skipped his sections as I found them really stupid and annoying, and I was glad when Komasan took over.
Komasan is a white dog from the countryside of Japan who moved to the big city which he knows nothing about. He's naive, innocent, and constantly amazed by things most people take for granted. He's very kind and polite, and really doesn't have a bad bone in his body.
Komajiro is an orange dog and Komasan's younger brother. Despite that, he knows and fits into the city better than Komasan does, though he still looks up to his big brother. He is more knowledgable and doesn't have the same innocence as Komasan, but is still more personable than Keita is.
There are many more characters, including another youkai who takes up residence at Keita's house, and Keita's friends (and love interest). However, they really don't do much except get possessed from episode to episode. I give this section a rating of "3.5"...one for Jibanyan, one for Komasan, one for Komajiro, and half for sometimes interesting other youkai (including Whisper and Robonyan).
I try to keep personal opinion out of my review until this point, though it sort of leaked into various spots.
The lack of a plot bothers me. I do understand that it's an episodic comedy anime, and any introduction of the plot can change that in a flash (such as Keita's friends finding out about youkai).
On the flip side, it's good for an upbeat (and often mindless) viewing since nothing of importance ever happens (with the exception of episodes 25 and 47, as well as the little "to be continued" shorts featuring Komasan).
I'd say that's probably the only reason to watch it...that, and if you want to see how some of your favorite youkai function out of the game. Most likely, you'll wind up either bored of it quickly or watching it only for Komasan's episodes.
Again, I found Keita to be one of the worst protagonists ever made. I thought Daisuke/Davis from Digimon Zero Two was bad...Keita is even worse. He literally has ZERO personality, and what he does have is that of a selfish kid.
Now, things like that are fine if they start out that way with a character and said character eventually starts to accept their role and evolve as a character...but Keita doesn't. Once in a blue moon he'll show perhaps slight concern for Jibanyan or feel bad for some youkai he encounters, and in one episode feels empathy for Kanchi/Eddie, but even after 70+ episodes, he's still the same brat as he was in the first episode.
This really takes away from the anime's overall likeability, since Keita is sort of the protagonist. Instead, I often will look forward to Komasan's features since those have more storytelling and character growth in them than the majority of the episodes Keita is in.
If you're bored, want a laugh, or want to watch a light-hearted anime, then I'd say take a look. Granted, if you worked and struggled to befriend some of those hard to get youkai in the game, you might get a little annoyed at how easily Keita gets their medals compared to what we have to do in the first game.
If you're looking for an anime with good, solid characters who grow and develop, or an anime with an interesting plot, then this isn't for you.
If you're looking for great characters and character growth and drama with youkai/the supernatural, I'd recommend Natsume Yuujinchou, instead.
If you're looking for great characters, plot, and action, along with supernatural elements, then I'd recommend Shaman King.
With the exception of Komasan's segments and some of Jibanyan's antics, this anime is really just good for background noise; you won't find a plot or any good (human) characters in this one, nor any drama (with the exception of episodes 25 and 47).
Like with the "characters" section, the Overall rating is as high as it is for the plots involving Komasan, and the amusement factor which comes with episodic comedy anime. I'd go so far as to say that Komasan carries the entire anime.