I've only played against it (the B-D Gambit) a handful of times, and every time I transposed to the French Defence (i.e. 1.d4 d5 2.e4 e6). When I look at B-D games it doesn't look particularly effective, but if there's a way of playing away from your opponent's pet line then it makes sense to do so.
It's got a bad rap for black because it's often played by beginners.
I just finished a game where a 1200 player challenged me & showed how not to play the center-counter as black
Game 3377852
😲
I play the Scandanavian as black against e-4, because it does normally take your opponent off their plan. I like to play the Icelandic gambit variation of it. Even if my opponent does try to convert it into a French opening, I will divert them back to my plan. It fits my particular style of play anyways. Cheers