Mmh, very interesting! I loved the way you wrote Gellert's PoV, because he feels (with more reason, but not a shred more modesty) very Lockhartian to me... *so* preoccupied with his own intelligence, so certain that the world revolves around him (and that Albus should, too), and absolutely immoral when it comes to respecting other people's lives. I liked his puzzlement that Albus might not be his rival, but his partner, and how hard it is for him to get his mind around that.
I loved Personally, Gellert thought that it was ridiculous for Albus to care for anyone but /him/, let alone an insane sister and a brother who seemed to never wash himself.
The Bathilda Bagshot plot was nice, too - good fic, mystery critter!