We have a potty (a big, cheap, plastic Wal-Mart bin) out on the large balcony. I want the dogs to ask to go outside, since we travel so much. I need their potty training to apply to hotels and places they don't have access to a potty. The potty is filled with Dr. Elsey's Long Hair cat litter crystals. I would not use anything else, personally. (I have a recent thread on this if you care to know more)
IF I ever went to an indoor potty, I'd get a CatGenie. Couldn't imagine using anything else in the apartment.