Despite appearances to the contrary (particularly the OVA, which did not convince me I wanted to watch it at all), this anime was anything but typical. [Except for the part where the male protagonist is the only normal human being in the whole series, but I have to ignore the "women are crazy" rhetoric in order to enjoy most things in life].
It's a harem. The two tsundere characters tsun-tsun'd all over each other more than they did over the main character, which was refreshing. The otaku/hikikomori imouto's two personalities were handled well. The main character was mostly completely unfazed by the ecchi jokes and naked gags, and the mad scientist never went unrealistically far in her attempts to seduce him. I WANT TO KNOW IF YUKIMURA REALLY IS A MALE! And Sister Maria was funny because of her childish gullability and foul mouth.
Anyway, the character balance here worked really well, imo. I'm not quite sure why--maybe due to banter, timing of gags, use of irony, nontypical reactions/endings to episodes--but it worked without any of the characters becoming too annoying, and I can't count the number of times I burst out laughing. The crowning achievement of the whole series is its irony to which the characters are completely oblivious: by joining a club in order to "practice the skills needed to make friends," they all end up making friends with each other.