The plot is about what you can expect from a slice of life - it's a silly premise, and the show only really comes into it's own once you've got the full character interaction.
I do really love the characters - they're extreme, likely more-so than any real people you'll find (at least, i hope this is the case...) but their personalities are not standard slice-of-life personalities. Yozora is extremely sadistic ... I'm not so sure I'd call her a tsundere, except for maybe a couple instances where she is actually nice. It doesn't happen that often. At the very least, she's not a normal tsundere...
Sena is a strange combo - very naive and borderline retarded at times, but also a genius as far as school work and athletics. Popular, with no friends. Might not make sense at a glance, until you watch.
Yukimura entertains me when "he" suddenly shows enthusiasm over something other than Kodaka. His seemingly gay interactions with Kodaka are pretty funny too... definitely one to create an awkward atmosphere.
Rika is ... well, damn. She's a huge pervert and has some mental problems, but makes me smile, and even laugh hysterically at certain points. (wait until the roller coaster... that's all I'll say) An actual genius, inventor, programmer, etc ... evidently she can do anything. She is also possibly the only one in the group who acknowledges that they're all friends.
Kobato has the whole Chuunibyou thing going on to the point that almost everything she says is "in character" ... it's cute, for some reason. Her hatred for Sena is great. I'd be scared of Sena too - not what you would call a "safe" person...
Maria ... well, she's annoying but still, cute. Also a genius, supposedly - but like most little kids, easy to trick and naive as can be. Also loud and impulsive - but she does add a necessary contrast to the rest of the group. Her little rivalry with Kobato makes me smile.
And well, Kodaka ... he's ok. He's definitely the weak link and so not worthy of a harem, he's a very standard and "safe" character. A very typical and boring pudding-head. I wouldn't really call him naive, but he's definitely scared by commitment and afraid to admit that he has friends. I found that aspect to be annoying, because unlike the other characters he doesn't have some extreme quirk keeping him from a social life or connecting the dots.
The art style is top notch. The characters look good, the backgrounds look good. It's all very full and detailed. Animation is about what you'd expect from a slice of life. Aside from the art style itself, there's nothing particularly eye popping - but the art style is very, very nice.
It's worth watching - especially if you want some non-standard humor and don't mind a little sadism. Full of insults and inappropriate comments ... it's a feel good anime, even if it's also one of the most mean-spirited you'll find. Maybe I've got that impression solely because of Yozora. Hmm. Well, it's got my approval. One of my favorites, in fact.
