Kept my feet warm this winter. The sole shows no sign of wear and is heavy nylon. The soles have enough insulation -- obviously the sole can't be puffy like the top, but it's insulated. Of course any puffy slippers feel a bit sloppy, but that's the price of keeping your feet warm.

The strap over the front of the ankle was not useful to me and may have put some pressure on the top of my feet. Inside, the edges of the soles are not finished smoothly, though this only matters when I wear them without socks, and I would not generally do that anyway.