Note that I am writing my thoughts and impressions of the show based off of episode one, so there is a chance that episodes 2 through 5 or the movie are much better.
I am an avid anime watcher/manga reader (from popular shows like Naruto to more obscure ones like Kindaichi Shounen no Jikenbo), so when I encountered a show that mixed western-style animation with anime, I got really excited. Unfortunately, my expectations were not met. The characters weren't very interesting, the animation looks like cheap flash animation, and the comedy wasn't anything new.
Almost all of the characters fit into some kind of stereotype. John is an average nice guy though a bit of a loser, Max is a lisping nerd, and Charity is the perpetually irritated and mean older sister. All of the adults have proved themselves completely useless and practically unnecessary for the plot. You could remove them and the episode would play out just the same save for a few jokes. Many of the background students are typical high school stereotypes (dumb jock, preppy girls, nerds, etc). Put simply, everyone is bland. However, I was willing to overlook this if the introduction of the anime characters would make the show much more entertaining than it was currently proving to be.
I did not understand the first thing that came out of Hiro's mouth. I understand what they were going for by having him say something really simple in a complicated way, but since I didn't know what he was trying to say in the first place, I didn't find it funny. After witnessing more of his behavior, Hiro felt like more of an exaggeration of what someone who has never seen anime before thinks anime characters are like. In other words, Hiro is an extremely overpowered and loud character armed with all sorts of laser weapons.
The animation here is rather... Johnny Test-y. I have seen flash animation done well (Wakfu), and this is nothing to write home about. I do like the anime characters' designs though. The hair is spot on.
The comedy in this is about as bland as everything else. There's some lame toilet humor, but most of the humor falls on Max and Hiro. Max is always acting like a slightly misogynistic nerd who is waaaay too invested in a card game and only talks about fantasy/nerd stuff. Basically, nothing that hasn't been done before. Hiro is always running around screwing things up with misunderstandings and his stereotype-ness. Again, nothing new. The only thing that made me laugh was when Hiro referred to his yelling as the way of his people. The show would be a lot funnier if it was more about the interactions between Hiro's stereotype and everyone else's stereotypes.
Perhaps episode 2 fixes things I have complained about, but as a start of a series, episode 1 of Exchange Student Zero is a disappointment.