It's hard to tell from your picture, but when you say "centipede," I'm thinking bristle worm. Google images of bristle worms and see if that's what you have. As far as good or bad, that's a matter of opinion....some like them as part of their CUC, other's hate them because of the "sting." FYI, don't try picking it up with bare hands.
It's definitely not a bristle worm, it's the segmented looking thing in the bottom portion of the goni in the picture I know it's hard to see it actually looks like a centipede like I even think that I looks like it has legs on it