I got the Wizdog because Buddy and his "family" were living in the kind of pen that has a grated bottom for them to pee and poop through - he transitioned to it really well - started using it immediately with a puppy pad under the grate. The added bonus is that the grate keeps them from being able to drag the pad around.
I don't think the grate is any harder than any floor and it does keep his feet drier.
There are certainly issues with it, though. You do need to clean the grate - I just put it in the bathtub about once a week or so and spray it with the shower hose. And if he has diarrhea I generally just put a potty pad across the top because otherwise it gets stuck in the grate and is kind of gross to clean...but in general I was very very happy with the purchase. Keeps the floor drier - but YYMV (Your Yorkie May Vary!)
I was thinking about getting another one...