Yeah I'm on the same boat. I've heard about dtilt -> jellyfish being a good combo but I never saw it myself. Pisces is really powerful but it's extremely gimmicky because it sends you flying off if you do connect it and that's really annoying; and it's also laggy and you can't cancel the animation/lag after you connect it the same way with bouncing fish. Another thing is that, if you hit people say, coming from the left side, you'd expect the move to send them to the right side.. but Pisces sends them to the left side, which really contradicts the fact that it's really powerful because it makes it really hard to actually hit people with it to kill them.
In addition to that you also lose some combos like fthrow > bf or fair > bf, although weak nair still combos into pisces.