I live in a central area, and anytime someone in our area does building work (extension on a house, etc), mice start showing up. We tried these for months and they sadly did not work. My husband had to go back to the old ones that kill them which I hate, but they were in my daughters room....so there wasn't a choice.
I think if they had a gripping surface on the bottom to stop them slipping and made them bigger that would help. These are quite small, more for field mice, not the large things that live downtown.