Yes, they will sometimes poop on the potty pad, but it depends on the dog and his/her "thing". A dog that feels the need to hide when they poo may be less likely to use it unless there's a tent/cover over it.
And "why would someone want the dog to go in the house"?
Meet Cleo:
She's 17 pounds with *very* thin fur and we live in the Snow Belt in Pennsylvania. She's also half Italian Greyhound-- a breed notoriously hard to house train because their natural submissiveness actually make asking for something from their owner intimidating/scary.
I would LOVE to get Cleo trained to a spot in the house. As it is, even after 18 months of working, she still prefers to use the bedroom floor if we're gone for more than 6 hrs., but she'll find a new spot when I put a puppy pad over her former accident sites. :hair: (We're still working on that.)
Another situation where indoor spot training comes in handy is with older dogs that can't handle steps well any more, especially large ones. A lot of people have their older dogs put to sleep or give them to rescues when they start having accidents in the house, when a little retraining to something like this could give them more happy years with their pet.
I wish we weren't so close to broke that $40 isn't happening this month, but the idea is something that would work very well for my family. Really it's not all that different than litter training a cat or a chinchilla.