Though with all that hate towards Kirino, I think she is a well-made character, as she is very unique and stand out(you don't see little sisters bitching on her brother very often in anime do you?), she's not the whiny "oniichan, oniichan" kind of sister you usually get. The best part of her is the actual annoyance she create, I seldomly know any heroine which specificly 'exist to annoy you' like Kirino. Most writers would want their heroine to be lovable and attractive to the audiences, but the author of OreImo decided to do the opposite, and it worked pretty nicely, though you still would want her to be alittle nicer and at least thank her brother properly for literally saving her existence
As for Kyousuke, I find his character highly unrealistic, he might look like the best existence you can ever have for a brother, but that is where it is illogical. Kyousuke had stated countless times that he hates Kirino, right from the beginning to the end, but he will go to extreme measures for her(SPOILER ALERT, skip the rest of this paragraph if you don't want to read spoilers) threatening to beat up his own father(which in turn could end up in him being beaten up himself and thrown out of the house for a week). Throwing away all his pride to beg to the animator team for Kirino's masturbation novel that he didn't even enjoy himself(which his and Kuroneko's rude attitudes towards them could've backfire them in the first place, normally if you talk like that to someone you want to please, chances are they won't be pleased and might even cancel out the anime project for it). Shaming himself countless times(acting like a total pervert for Ayase to make up for her friendship with Kirino, buying eroge in front of a huge crowd, seen by his own best friend and some other townspeople who show outright disgust to him), etc and YET he is willing to continue being Kirino's slave when he fully have the right to kick Kirino for his own frustration.
For the other supporting/minor characters, many are too bland, illogical, or simply not appealing enough. Ayase, Kuroneko and Saori became close to Kyousuke for no particular reason(well there is a reason and it is: he needs a harem). Manami is the only girl who is reasonable enough to be romanticly involved with Kyousuke and yet the story would intentionally kill her charm by calling her mundane by itself, which would have raised her appeal if the story have just left those sentences out(well they have to tone her down so the harem could happen, otherwise she would officially be Kyousuke's legal wife and no other girl could be paired with him), and another character featured in the OVA, Akagi Sena, Kyousuke's friend's little sister, had showed severe obsession on yaoi, to the extent that it impaired her logic and moral to be stupid enough to present an idea on a yaoi game in a room full of straight guys, not noticing that it could as well get her kicked or expelled from the club, if not school.
In conclusion this series is decent if you want to watch something while turning your brain off, ignoring all the illogical points and enjoying the nonsense of a seemingly masochistic brother being beaten by his sadistic little sister, but well if you don't like anime that annoy you, whether or not you like tsunderes or not, you should stay away from this anime just to keep your nerves intact.
