I love this stuff, and won't be without it.
It's not a miracle worker. Not much is. But it cleans and shines stainless unlike any other thing I've ever used. I clean my sink with it every couple of days, and my stainless pots and pans with every use.
I've found that if you have really dirty stainless pans, burned on stuff for years, you need to soak them in oven cleaner in a garbage bag overnight, then once clean, keep them clean using the bio cleaner with every washing, and no old build up for the future.
I use it on our fiberglass showers sometime, bathroom sink and fixtures too. It cleans glass and ceramic that gets stuck on foods, or water spotted as well too.
I don't have an issue with how hard the clay is, I wet the sponge and wipe it over the top of the clay. It actually works better if it isn't too wet and runny, but a bit on the dry side anyway.