I've tried comet and it started to scratch the surface. Even soft scrub scratched the porcelain (is that what it is?) Comet and Mr. Clean are my two big weapons. I love how Mr. Cleans smells and a bottle of it lasts forever (unless the kids use it and its gone in one afternoon... the concept of it ebing concentrated is completely lost on them )

I have tried to not use ammonia because of the cats - since their pee has amonia in it, I've always been afraid they'll try to spray where I've cleaned with amonia to leave their own mark.