BBB has all the elements that bugs me about Futurama. With Futurama, the story is always more important than the characters, and the characters are bent, folded and twisted to fit the story no matter what. Thus, when the characters are thrust into wildly improbable situations (not that there's anything fundamentally wrong with that, this being a cartoon and all), we, the viewers, have no reference point from which to be either amused or astounded. We have no one character to identify with, since none of them, for the most part, act even remotely believably human. I think that one identifiable character is essential for any work of fiction, cartoon or otherwise. In The Simpsons, that one character is probably Marge. In King of the Hill, that one character is probably Hank. In Fairly Oddparents, that one character is (or should be) Timmy. Of course, ideally, all the characters in a given cartoon should have some aspect we all recognize, identify with or sympathize with. Spongebob has three such characters: Spongebob himself, due to his innocent, childlike optimism; Squidward, due to his dour attitude towards his unfulfilling grunt job and his equally unfullfilled dreams; and Mr. Krabs, because of his kindly but practical "Stop-dreaming-and-work-for-a-living" credo. All 3 have some human quality we the viewers recognize. But nobody in Futurama really has those qualities. They're all very superficial. Even Leela seems rather cold and distant, although she's easily the smartest and most competent of the bunch.
Really, you'd think that, given his fish-out-of-water persona, Fry would be the identifiable character in the Futurama universe. But he's just as off-kilter and puzzling as the rest of them. The only thing that makes him remotely sympathetic is his obsession with Leela. And sadly, that aspect was completely left out of BBB. Because of that, while watching Fry, I felt like I was watching a stranger. And I don't think the idea behind the special, and the jokes it generated, really made up for it.
Didn't mean to write an essay here, but anyway, that's my take on BBB.