Haha sorry, I guess I'm still a little bitter that one of my favourite expository dialect-providing series basically turned into a fanwank. I don't blame Senjougahara for cutting her hair and trying to get his attention in a different way; even threatening him with infinite pain doesn't turn his eyes away from his own damn sister.
But in all serious, I don't see Koyomi as a Gary Stu so much as I see him as The Man with 1,000 Personalities (each perfectly attuned to each member of his harem ). An anime blogger once joked that Koyomi would probably explode from personality clashes if there was ever a scene involving him and three or more of his harem members. I'm inclined to agree, lol.