when I opened this thread I was listening to old Slayer, which depended heavily on double bass for it's impact. Of course early Metallica doesn't use a lot of double-bass so it really depends on the rest of the music and what kind of sound you're going for. Mostly I listen to a lot of doom and sludge which hardly uses double bass at all. As this is mostly what I've been playing my own skills have declined lately.

When I played grind I was a big fan of it for certain parts, but I still mostly used only the single petal.