OBIT: After 6...Bxf2+ 7. Kxf2 Ng4+:
If 8. Ke1 then 8...Ne3 9. Qh5 (or 9. Qe2/f3 Nxc2+ followed by 10...Nxa1, winning material) Nxc2+ looks promising for Black, one key tactical point being 10. Kd1? Bg4+! 11. Qxg4 Ne3+. Since 10. Kf1 or 10. Kf2 would allow 10...Qf6+ followed by 11...Nxa1, 10. Ke2 has to be the best try. At this point, Black can decide whether to play gambit-style with something like 10...Nc6 11. Rb1 O-O (he has two pawns for a piece and White's position is a mess - seems like a good deal) or go for material advantage with 10...Nxa1 11. Qxe5+ Kf8, when trapping the Black knight looks awkward. In the latter line, I think at worst Black will come out with a rook and two pawns for two pieces.
Having said that, I don't see what's so bad about 8. Ke2(!). Black only gets one pawn for the piece, and the position of the White king isn't as uncomfortable as it may look at first glance. So, <MorphyMatt>, I'm inclined to agree with you - the bishop sac in this game doesn't seem sound.