The plot starts off in a very unique manner, but then quickly goes downhill from there. First, the girl rejects the guy. Then the guy rejects the girl. Then it switches. Again. And Again. And again. And aga- You get the point. I saw quite a bit of potential in this series during the first few episodes, but after that, this show became a typical rom-com with rivals in romance appearing for both protagonists. Kaibutsu-kun's inability to take things seriously put me off the most. Issues that should have been resolved maturely, are instead ignored/interrupted/forgotten through the unpredictable and ridiculous acts of the main guy.
The character designs are simple yet fitting. I'd say quality is about average, as motions and backgrounds are basic. I don't have anything else to say.
The opening is okay and the ending is unremarkable. The voice acting is not bad. I think Shizuku's (female protagonist's) voice is the best/very fitting (just love how her voice always seems full of cynicism).
The concept of a loner girl who enjoys studying is interesting. I can't say the nice but scary looking guy is original (look at Ryuuji from Toradora), but he is apparently very smart so that somewhat sets him apart from other characters like him. Unfortunately, his intelligence just seems like a plot device to piss Shizuku off at times.
Shizuku seems to develop a little, but she's so inconsistent, that I'm not sure. On the other hand, the guy (still can't remember his name) doesn't develop at all.
Other characters aren't anything special, as the show mostly resolves around the couple's (rocky, sometimes to the point of being annoying) relationship.
Although I find the way the show started off interesting and original, you should watch only if you're bored and completely out of other rom-coms to watch.
Note: To people interested in the manga: Don't quote me on this, but I heard that the anime branches off from the manga around episode 4, which could explain the drop in quality of the story.