From Houndeye anuses to niggling about cyclic rates of various HL weapons models, it may just be that the BM forums have covered everything possible about BM while waiting for the game.
Or maybe not…
What have we missed? Headcrab mating rituals? G-Man eye color changes? Enemy AI subroutine management? Shell casing duration in the game world? Possible changes in Gordon’s sexual orientation from HL to BM?