Yes, I've tried marine snow, but only because it was free. I would never buy the stuff. I never saw any difference in anything. Corals are carnivores and they're picky about the size and taste of their food. Liquid feeds don't do much for them since in most cases the particles aren't the right size or composition.
Cyclop-eeze is copepods, which are food for lots of things in the ocean including corals. Not all corals will benefit from cyclop-eeze though since it's too big for many. Like paintbug said, other types of zooplankton such as rotifers and BBS are great foods as well, especially for corals with smaller mouths.